GENERAL ARTICLES

GENERAL ARTICLES
CURRENT SCIENCE, 1492 VOL. 92, NO. 11, 10 JUNE 2007
†The views expressed in this article are solely those of the authors, and
do not represent those of the Department of the Navy or any of its
components, or the Institute for Defense Analyses.

Ronald N. Kostoff and Raymond G. Koytcheff are in the Office of
Naval Research, 875 N. Randolph Street, Arlington, VA 22217, USA
and Clifford G. Y. Lau is in the Institute for Defense Analyses, 4850
Mark Center Drive, Alexandria, VA 22311, USA.
*For correspondence. (e-mail: kostofr@onr.navy.mil)

Global nanotechnology research literature
overview†
Ronald N. Kostoff *, Raymond G. Koytcheff and Clifford G. Y. Lau
Text mining was used to extract technical intelligence from the open source global nanotechnology

and nanoscience research literature (SCI/SSCI databases). The following were identified: (i) the

nanotechnology/nanoscience research literature infrastructure (prolific authors, key journals/
institutions/countries, most cited authors/journals/documents); (ii) the technical structure (pervasive
technical thrusts and their inter-relationships); (iii) nanotechnology instruments and their relationships;
(iv) potential nanotechnology applications; (v) potential health impacts and applications,
and (vi) seminal nanotechnology literature. The results are summarized in this article.

Keywords: Bibliometrics, document clustering, nanoparticle, nanotechnology, nanotube, text mining.
NANOTECHNOLOGY is booming! In the global fundamental
nanotechnology research literature as represented by the
Science Citation Index/Social Science Citation Index (SCI/
SSCI)1, global nanotechnology publications have grown
dramatically in the last two decades.

Due to this exponential growth of the global nanotechnology
open literature, there is a need for gaining an
integrated quantitative perspective on the state of this literature.
In 2003–05, a comprehensive text-mining study

was performed to survey the technical structure and infrastructure
of the global nanotechnology research literature,
as well as the seminal nanotechnology literature2,3. Based
on the wide-scale interest generated by these reports, it
was decided to update and expand the study using more recent
data, a much more comprehensive query and more
sophisticated analytical tools.

In the updated study, text mining was used to extract
technical intelligence from the open source global nanotechnology
and nanoscience research literature (SCI/SSCI
databases). The following were identified: (i) the nanotechnology/
nanoscience research literature infrastructure
(prolific authors, key journals/institutions/countries, most
cited authors/journals/documents); (ii) the technical structure
(pervasive technical thrusts and their inter-relationships);
(iii) nanotechnology instruments and their relationships;
(iv) potential nanotechnology applications; (v)
potential health impacts and applications, and (vi) seminal
nanotechnology literature. The results are summarized in
this article. A more detailed report on the results and
methodologies of this updated study can be found in
Kostoff et al.4.
This article is an overview of the highlights of the total
study, including the production efficiency of seminal
nanotechnology documents. The results are divided into
four main sections: Infrastructure, Technical structure,
Instrumentation and Applications. The Applications section
is further divided into non-medical and medical. The
results will be presented in the order listed above. Next,
the seminal nanotechnology literature production efficiency
will be presented.
Infrastructure describes the performers of nanoscience/
nanotechnology research at different levels, ranging from
individual to national performers, and it includes archived
literature as well. Technical structure identifies the pervasive
technical thrusts (and their inter-relationships) of the
nanoscience/nanotechnology literature. Instrumentation
provides both infrastructure and technical structure of the
subset of the nanoscience/nanotechnology literature that
addresses specific instruments. Applications provides the
infrastructure and taxonomy of the subset of the nanoscience/
nanotechnology literature that addresses specific
non-medical and medical applications.

Approach

An extensive nanotechnology/nanoscience-focused query
(300 + terms) was applied to the SCI/SSCI database. The
nanotechnology/nanoscience research literature technical
structure (taxonomy) was obtained using computational
linguistics, especially document clustering. The nanotechnology/
nanoscience research literature infrastructure
(prolific authors, key journals/institutions/countries, most
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CURRENT SCIENCE, VOL. 92, NO. 11, 10 JUNE 2007 1493
cited authors/journals/documents) for each of the clusters
generated by the document clustering algorithm was obtained
using bibliometrics.
The instrumentation literature associated with nanoscience
and nanotechnology research was examined. About
65,000 nanotechnology records for 2005 were retrieved
from the SCI/SSCI, and ~27,000 of these were identified
as instrumentation-related. All the diverse instruments
were identified and their associated documents categorized
in a hierarchical taxonomy. Metrics associated with
research literature for specific instruments/instrument groups
were generated.

The applications literature associated with nanoscience
and nanotechnology research was examined. Through visual
inspection of 60,000 of the abstract phrases of the same
downloaded 2005 records, all the diverse non-medical
applications were identified and their associated documents
categorized in a hierarchical taxonomy. Metrics associated
with research literature for specific applications/applications
groups were generated.

For medical applications, a fuzzy clustering algorithm
(where a record could be assigned to multiple clusters) was
applied to the downloaded 2005 records. A sub-network
that encompassed all the medical applications was identified.
Again, metrics associated with research literature for
specific medical applications were generated.

Results

Infrastructure

Country publications:

· Global nanotechnology research article production
exhibited exponential growth for more than a decade
(Figure 1).

· The most rapid growth over that time period came
from East Asian nations, notably China and South Korea
(Figure 2).

Figure 1. SCI/SSCI articles vs time: total records retrieved.
· Some of this apparent rapid growth (in China, for
example) is partially due to (i) a country’s researchers
publishing a non-negligible fraction of total papers in
domestic low impact factor journals, and (ii) these
journals being accessed recently by the SCI/SSCI, rather
than due to growth based on increased sponsorship or
productivity.

· China’s representation in high impact factor journals


· From 1998 to 2002, China’s ratio of high impact nanotechnology
papers to total nanotechnology papers
doubled, placing the country at parity for this metric
with the advanced nations of Japan, Italy and Spain.
· The US remained the leader in aggregate nanotechnology
research article production.
· In some selected nanotechnology sub-areas, China had
achieved parity or taken the lead (see Figure 3 for the
nanocomposites example).
Figure 2. Country comparison time trend (number of articles vs time).
Figure 3. Number of papers containing ‘nanocomposite’*.
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CURRENT SCIENCE, 1494 VOL. 92, NO. 11, 10 JUNE 2007
· South Korea started even further behind China in both
total nanotechnology publications and highly cited
papers, but has advanced rapidly to become a secondtier
contender in total and highly cited papers.
Country citations:

· There was a clear distinction between the publication
practices of the three most prolific Western nations
(USA, Germany, UK) and the three most prolific East
Asian nations (China, Japan, South Korea). The Western
nations published in journals with almost twice the
weighted average impact factors of the East Asian nations.
Much of the difference stems from the East Asian
nations publishing a non-negligible amount in domestic
low impact factor journals, while the Western nations
publish in higher impact factor international journals.
· Two countries that led in production of the most cited
nanotechnology papers were the US (126) and Germany
(31). They accounted for 40% of the most cited
nanotechnology papers.

· The high paper volume production East Asian countries
of China and South Korea accounted for 2% of the
most cited nanotechnology papers.
· Despite the increased paper productivity from East
Asian countries, the US continued to generate the most
cited nanotechnology papers.

Technical structure

The total retrieved nanotechnology database for 2005 was
examined from four perspectives to identify pervasive
thematic thrusts: document clustering, autocorrelation mapping,
factor analysis and cross-correlation mapping. Each
perspective provided valuable insights on the fundamental
nanotechnology literature structure. Only document clustering
results are presented here.

Document clustering: The database was divided into
256 thematic clusters by the clustering algorithm. USA
produced most papers in 169 thrusts, China led in 70, Japan
led in 15, and India, South Korea and Spain each led in
one.
A hierarchical taxonomy was constructed from these
256 elemental clusters. Of the sixteen fourth-level categories
in taxonomy, China was the publication leader in six.
Specifically, China led in: Properties of thin films; Diamond
films; Applications of carbon nanotubes; Multiwalled
nanotubes; Nanomaterials and nanoparticles, and
Polymers, composites and metal complexes (Figure 4;
categories with solid shading denote publication lead by
China, and those with vertical lines and shading denote
publication lead by Japan. Light shading means category
leader has 100–125% of the USA publications; medium
shading 125–150%; dark shading >150%). Essentially,
China led in the materials and nanostructures component
of the database, whereas USA led in the physical science
phenomena and biomedical components.
Instrumentation
A wide variety of instruments are used in nanoscience
and nanotechnology research. Key among these are X-ray
diffraction (XRD), electron microscope variants, atomic
force microscopy, scanning tunnelling microscopy and
spectroscopy variants.
LEVEL 1 LEVEL 2 LEVEL 3 LEVEL 4
Quantum phenomena Quantum dots (2028 records)
(3326 records) Quantum wells, Wires, and States (1298
records)
Optics and Electronics (16,432 records)
Quantum phenomena,
Optics, Electronics,
Magnetism, and Tribology
(26,077 records) Optics, Electronics, Magnetism, and
Tribology (22,751 records) Magnetism and Tribology (6319 records)
Thin films (4760 records) Properties of thin films (2251 records)
Applications of thin films (2509 records)
Deposition of thin films (1752 records)
Quantum phenomena,
Optics,
Electronics,
Magnetism,
Tribology, and
Films (32,983
records)
Films (6906 records)
Deposition of films (2146 records)
Diamond films (394 records)
Applications of carbon nanotubes (474
records)
Multi-walled nanotubes
(2350 records)
Multi-walled nanotubes (1876 records)
Single- and double-walled nanotubes (447
records)
Nanotubes (3211 records)
Single-walled nanotubes
(861 records)
Single-walled nanotubes (414 records)
Nanomaterials, Nanoparticles, Poly- Nanomaterials and Nanoparticles (14,263 records)
mers, Composites, and Metal complexes
(22,686 records)
Polymers, Composites, and Metal Complexes
(8423 records)
DNA (775 records)
Nanotubes, Nanomaterials,
Nanoparticles,
Polymers,
Composites, Metal
complexes, and
Bionanotechnology
(31,742 records) Nanomaterials, Nanoparticles,
Polymers, Composites,
Metal complexes, and Bionanotechnology
(28,531
records)
Bionanotechnology (5845 records)
Proteins and Cellular components (5070 records)
Figure 4. Four-level hierarchical taxonomy.
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NMR, Complexes, Com- NMR, Spectroscopy (306)
pounds (1546) NMR, Complexes, Compounds (1240)
DSC (1138)
NMR, RS,
Calorimetry
(4684) RS, Calorimetry
(3138) Raman scattering, RS, AFM
(2000)
AFM, Films, Tip, Imaging AFM, Film, Tip, Imaging (1055)
(2003) AFM, Film, Substrate, Deposit (948)
AFM, Film, Deposit, Substrate, Growth (1511)
AFM,
NMR,
Calorimetry
(8423)
AFM (3739)
AFM, Films, Deposition,
Growth, Substrate (1736) AFM, Magnetic (226)
TEM (2545) HRTEM (296)
TEM (2249)
SEM, Film, Particle, Cell (1652)
EM (4492)
SEM, Films, Composites,
Particles, Cells (1947) SEM, IS (295)
SEM, XRD, Films, SEM, XRD (1451)
Coatings, Composites
(3634)
SEM, Film, Coating, Deposit, XRD (2183)
TEM, Film, Particle, Nanoparticle, STM (5986)
EM, XRD
(19,090)
XRD, Films
(14,598)
XRD, TEM, Thin films
(10,964) Film, XRD, XPS (4978)
Figure 5. Nanotechnology instrumentation taxonomy. AFM, Atomic Force Microscopy; NMR, Nuclear Magnetic Resonance;
EM, Electron Microscopy; XRD, X-Ray Diffraction; RS, Raman Spectroscopy; TEM, Transmission Electron
Microscopy; HRTEM, High Resolution Transmission Electron Microscopy; SEM, Scanning Electron Microscopy; DSC,
Differential Scanning Calorimetry; IS, Infrared Spectroscopy, and STM, Scanning Tunnelling Microscopy.
Instrument taxonomy: Hierarchical taxonomy offered the
following insights:
· In this nanotechnology instrumentation study, China
produced about 25% more papers than the USA (Figure 5;
shading represents China’s publication leadership;
darker shading represents stronger publication leadership).
By contrast, in the full nanotechnology study,
USA produced about 25% more papers than China.
· Much of China’s over-production occurred in the XRDrelated
categories, but there was some over-production
in transmission electron microscopy and NMR and
calorimetry-related categories as well.
· The US dominance was in atomic force microscopy.
· Because of the large Chinese and South Korean contributions
to the nanotechnology instrumentation literature,
author-name analysis at aggregate levels was
not effective; Asian names are usually monosyllable,
many times with no middle names. Due to the relatively
high frequency of paper publications, there is good
possibility that the same last name represents multiple
authors. Potential name disambiguation is under study.
· Even though USA has a large presence overall, relatively
few US institutions were listed among the most
prolific in the nanotechnology instrumentation papers.
The Asian and European efforts appeared concentrated
in relatively few but large institutions.
Applications
The study also identified the main nanotechnology applications,
both medical and non-medical, as well as the related
science and infrastructure. These relationships will
allow the potential user-communities to become involved
with the applications-related science and performers at
the earliest stages, to help guide the science conversion
towards specific user needs most efficiently.
Non-medical applications: Applications thrust areas –
Factor analysis.
Factor analyses were performed to show the thematic
areas in non-medical applications. A six-factor analysis
showed the following themes:
· Factor 1: Optoelectronics
· Factor 2: Tribology
· Factor 3: Lithography
· Factor 4: Control systems
· Factor 5: Devices
· Factor 6: Microsystems.
Applications thrust areas – Factor analysis and visual inspection.
The main non-medical applications thrust areas identified
above were augmented by important but non-networked
thrusts, and the nine resulting themes were related to science
and infrastructure by co-occurrence matrices. Also,
the total non-medical applications was combined into one
unit, and related to science and infrastructure by cooccurrence
matrices. For non-medical applications:
· USA led in total non-medical applications publications
and in six out of nine themes in high-tech research
areas such as devices, sensors and lithography.
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China led in publications in three traditional areas: catalysis,
tribology and electrochemistry.
· In total non-medical applications, two of the top three
institutions were Chinese. However, USA was well
represented by the large State University systems of
the University of California and University of Illinois.
· The journal Applied Physics Letters appeared in the top
layer in seven of the nine themes and was by far the
leader in total non-medical applications publications.
Journal of Physical Chemistry B appeared in four of
the nine themes, as also Journal of Applied Physics.
Medical applications: Applications thrust areas –
Visual inspection/fuzzy clustering.
A medical applications categorization constructed from
visual inspection of the detailed fuzzy clustering categories
showed five broad thematic categories:
· Cancer treatment
· Sensing and detection
· Cells
· Proteins
· DNA.
Applications thrust areas – Fuzzy clustering.
For medical applications, analysis of nineteen thematic
categories obtained from fuzzy clustering of the total
2005 nanotechnology database revealed the following:
· USA was the publication leader in total health types,
and in all the thematic areas as well, mostly by a wide
margin. China was the second most prolific in seven
thematic areas, Japan in six, Germany in four and
England in two.
· The University of California system led in five clusters,
the Chinese Academy of Science led in four, and the
National University of Singapore led in three. The
University of California and the Chinese Academy of
Science were the most prolific in the non-medical applications
as well, but their orders were reversed. The
National University of Singapore was a prolific contributor,
especially in pharmaceuticals and biomaterials.
· The journal Langmuir contained the most nanotechnology
articles in total health, and was in the top layer of
ten of nineteen themes. The only journals in common
in the top layers of applications and health were Langmuir
and Journal of Physical Chemistry B.
Production efficiency of global nanotechnology
literature
The global nanotechnology research literature has two
main components: spatial and temporal. The spatial component
covers present-day nanotechnology research being
conducted globally. The temporal component reflects the
impact that vintage literature has had on modern-day
nanotechnology research.
Both the temporal and spatial components need to be
understood for full comprehension of global nanotechnology
research, and for the establishment of strategic
nanotechnology policy. Assessment tools and processes
have advanced sufficiently to allow an integrated picture
of nanotechnology to be obtained.
The summary material presented earlier concentrates
on the spatial component. The remainder of this article
will concentrate on one aspect of temporal component,
production efficiency of the seminal nanotechnology literature.
All the nanotechnology documents published between
1991 and 2005 were downloaded. Then, the subset with
the highest number of citations was extracted, and a text
mining analysis of that subset was performed to obtain
the characteristics of the most cited nanotechnology documents4.
Following this, the relationship between document
production and seminal paper production for
countries was identified.
Relation of seminal nanotechnology document production
to total nanotechnology document production: There is
a substantial value in understanding the efficiency of seminal
nanotechnology document production, i.e. the ratio of
seminal nanotechnology documents produced to over-all
nanotechnology documents produced. The present short
section addresses some methods for arriving at this ratio.
Citations (and publications) for nanotechnology documents
published in two specific years were examined.
The purpose was to obtain some time trend data as well
as better statistics than one year’s data could provide. All
nanotechnology documents for 1998 and 2002 were retrieved
and analysed. These years were selected to be as
close to the present as possible, in order to insure currency
of findings, yet sufficiently vintaged to insure accumulation
of adequate citations.
Normalized country production of seminal nanotechnology
papers: The main nanotechnology query in this
study4 was used to retrieve documents from the SCI/SSCI
for 1998 and 2002. Distribution of number of publications
among institutions and countries was generated using
the Analyze function of the SCI search engine. Then, the
publications for each year were ordered according to
Time cited. The most highly cited publications were extracted,
and the country and institution distributions for
those documents were generated. The country and institution
publication distributions were then compared to the
citation distributions. This allowed identification of countries
whose citation fractions were greater than their publication
fractions (and thus were producing highly cited
papers more efficiently than their publication statistics
would predict).
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CURRENT SCIENCE, VOL. 92, NO. 11, 10 JUNE 2007 1497
A central issue was how one defines most highly cited
papers. Are these seminal papers the top 10, top 100 or
top 1%? Because of the discrete choice imposed by the
Analyze function at present, results for the top 100, 250
and 500 documents were examined parametrically. While
some re-ordering occurred, countries producing seminal
documents were plainly evident at the top of the list.
Therefore, results using the 500 most cited documents
(about 1% of the total documents retrieved for 2002, and
about 1.5% of the total documents retrieved for 1998) are
presented.
Table 1 shows the country distributions for 1998. The
left column in Table 1 shows ranking according to a
country’s total nanotechnology publications in 1998. For
example, in 1998 USA produced 25.99% of the total
nanotechnology publications. The right column in Table
1 shows ranking according to a country’s representation
on most highly cited papers. For example, USA was represented
on 58.8% of the 500 most highly cited nanotechnology
papers published in 1998.
Table 1. Country distributions – Overall records/500 most cited
records (1998)
Country rank by most cited
Country rank by total publications records (121 cites min)
Country Percentage Country Percentage
USA 25.99 USA 58.80
Japan 15.72 Germany 12.20
Germany 13.72 Japan 9.60
France 7.73 France 8.00
England 6.93 England 7.80
P. R. China 6.10 Switzerland 4.20
Russia 4.87 The Netherlands 3.20
Italy 3.89 Canada 2.40
Spain 3.02 Israel 2.40
South Korea 2.96 Italy 2.20
Canada 2.81 Sweden 1.80
Switzerland 2.44 Spain 1.60
India 2.31 Australia 1.40
Sweden 2.13 P. R. China 1.40
The Netherlands 1.88 Austria 1.20
Poland 1.68 India 1.00
Taiwan 1.63 Russia 1.00
Australia 1.52 Denmark 0.80
Belgium 1.32 Ireland 0.80
Israel 1.27 Belgium 0.60
Brazil 1.20 Brazil 0.40
Denmark 0.94 Finland 0.40
Austria 0.89 Hong Kong 0.40
Ukraine 0.78 Hungary 0.40
Scotland 0.76 Scotland 0.40
Mexico 0.71 South Korea 0.40
Czech Republic 0.69 Croatia 0.20
Finland 0.67 Czech Republic 0.20
Hong Kong 0.66 North Ireland 0.20
Hungary 0.65 Norway 0.20
Singapore 0.65 Poland 0.20
Thus USA was both the most prolific nanotechnology
publishing country and most represented country on
highly cited nanotechnology papers for 1998. Its ratio of
per cent representation on most highly cited nanotechnology
papers to per cent of total nanotechnology publications
(ratio = 58.80/25.99) was 2.26. A ratio greater than one
indicates that a country has higher representation on most
cited papers than would be expected from its publications
alone. A ratio less than one indicates that a country has
lower representation. A ratio of 2.26 for USA indicates
that the country’s representation on most highly cited records
is 2.26 times what would be expected based on
nanotechnology publications alone.
None of the other producers has ratios approaching that
of USA (for 1998 publications), and only some of the
smaller hi-tech countries (Switzerland, the Netherlands,
Israel) had ratios that only remotely approach that of USA.
Table 2. Country distributions – Overall records/500 most cited
records (2002)
Country rank by most cited
Country rank by total publications (80 cites min)
Country Percentage Country Percentage
USA 24.02 USA 58.20
Japan 15.09 Germany 11.40
P. R. China 11.62 Japan 8.40
Germany 11.55 England 6.20
France 7.43 P. R. China 5.80
England 5.86 France 5.40
Russia 4.83 South Korea 3.80
South Korea 4.45 Switzerland 3.40
Italy 3.92 Canada 2.80
Spain 3.09 The Netherlands 2.20
India 2.89 Italy 2.00
Canada 2.40 Spain 2.00
Taiwan 2.18 Sweden 2.00
Sweden 2.05 Finland 1.40
Poland 1.92 Belgium 1.20
Brazil 1.91 Brazil 1.20
Switzerland 1.80 Denmark 1.20
The Netherlands 1.77 Russia 1.20
Australia 1.54 Australia 1.00
Belgium 1.26 Austria 1.00
Israel 1.25 Israel 1.00
Singapore 1.22 Scotland 0.80
Austria 1.02 Singapore 0.80
Ukraine 0.99 Taiwan 0.60
Mexico 0.81 India 0.40
Scotland 0.78 Ireland 0.40
Czech Republic 0.78 Portugal 0.40
Finland 0.73 Argentina 0.20
Denmark 0.69 Czech Republic 0.20
Portugal 0.62 Greece 0.20
Hungary 0.59 Hungary 0.20
Greece 0.56 Lithuania 0.20
Turkey 0.51 Mexico 0.20
Argentina 0.46 Poland 0.20
Romania 0.45 Slovenia 0.20
Bulgaria 0.31 Turkey 0.20
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CURRENT SCIENCE, 1498 VOL. 92, NO. 11, 10 JUNE 2007
Countries that have exhibited rapid growth in SCI/SSCI
nanotechnology paper production in recent years (e.g.
China, South Korea) have ratios an order of magnitude
less than that of USA (for 1998).
Table 2 shows the same type and structure of data as
Table 1, but for 2002. The USA remains dominant in nanotechnology
publications and representation on most
highly cited nanotechnology papers, with a ratio of 2.42.
A few of the smaller Central/Northern European countries
(Switzerland, Finland, Denmark) have ratios on the
order of two, and form the second ratio tier after the
USA. Norway, the third member of the small Scandanavian
countries, has about 1/3 the publications of Finland/
Denmark, and has no representation on the 500 most
cited papers list, in line with its relatively poor citation
performance shown in our Finland country assessment
study5.
A number of countries retain the same ratio as in 1998
(within 10%), including the USA, Germany, Japan, England,
Switzerland, Italy and Spain. China’s ratio doubled to
about 0.5, placing it on parity with Japan, Italy and Spain
for this metric. In a recent study by the first author6, it
was shown that China’s growth of papers in high impact
factor journals was faster than its rate of overall publication
growth, and that conclusion may be reflecting itself
in the present numbers. South Korea’s ratio jumped even
more dramatically from 1998. Russia’s, Taiwan’s and
Poland’s ratios remain low, and India’s ratio decreased
substantially to join this latter group for 2002.
1. SCI, 2006, Certain data included herein are derived from the Science
Citation Index/Social Science Citation Index prepared by the
THOMSON SCIENTIFIC® Inc. (Thomson®), Philadelphia, Pennsylvania,
USA; ©Copyright THOMSON SCIENTIFIC® 2006. All
rights reserved.
2. Kostoff, R. N., Stump, J. A., Johnson, D., Murday, J. S., Lau, C. G.
Y. and Tolles, W. M., The structure and infrastructure of the global
nanotechnology literature. J. Nanopart. Res., 2006, 8, 301–321.
3. Kostoff, R. N., Murday, J. S., Lau, C. G. Y. and Tolles, W. M., The
seminal literature of global nanotechnology research. J. Nanopart.
Res., 2006, 8, 193–213.
4. Kostoff, R. N., Koytcheff, R. G. and Lau, C. G. Y., Structure of the
global nanoscience and nanotechnology research literature. DTIC
Technical Report (http://www.dtic.mil/). Defense Technical Information
Center, Fort Belvoir, VA, USA, 2007.
5. Kostoff, R. N., Tshiteya, R., Bowles, C. A. and Tuunanen, T., The
structure and infrastructure of the finish research literature. Technol.
Anal. Strategic Manage., 2006, 18, 187–220.
6. Kostoff, R. N., Briggs, M. B., Rushenberg, R., Bowles, C. and
Pecht, M., The structure and infrastructure of Chinese science and
technology. DTIC Technical Report (http://www.dtic.mil/). Defense
Technical Information Center, Fort Belvoir, VA, USA, 2006.
Received 1 February 2007; revised accepted 16 February 2007