Prof.dr. Ludo Waltman

Ludo Waltman is professor of Quantitative Science Studies and scientific director at the Centre for Science and Technology Studies (CWTS) at Leiden University. He is a coordinator of the Information & Openness focal area and a member of the Evaluation & Culture focal area. Ludo is co-chair of the Research on Research Institute (RoRI).

Ludo’s work focuses on studying and developing infrastructures, algorithms, and tools to support research assessment, science policy, and scholarly communication. Ludo is open science ambassador of Leiden University, member of the board of ASAPbio, chair of the advisory board of OpenCitations, and coordinator of the Initiative for Open Abstracts (I4OA). Together with his colleague Nees Jan van Eck, Ludo has developed the well-known VOSviewer software for bibliometric visualization. Ludo is coordinator of the CWTS Leiden Ranking, a bibliometric ranking of major universities worldwide. In addition, Ludo served as Founding Editor-in-Chief of the journal Quantitative Science Studies.

Publications

Journal publications (78)

• Colavizza, G., Costas, R., Traag, V.A., Van Eck, N.J., Van Leeuwen, T.N., & Waltman, L. (2021). A scientometric overview of CORD-19. PLoS ONE, 16(1), e0244839. (paper)
• Lamers, W.S., Boyack, K.W., Larivière, V., Sugimoto, C., Van Eck, N.J., Waltman, L., & Murray, D.S. (2021). Meta-Research: investigating disagreement in the scientific literature, e72737. eLife, 10. (paper)
• Visser, M.S., Van Eck, N.J., & Waltman, L. (2021). Large-scale comparison of bibliographic data sources: Scopus, Web of Science, Dimensions, Crossref, and Microsoft Academic. Quantitative Science Studies, 2(1), 20-41. (paper)
• Subelj, L., Waltman, L., Traag, V.A., & Van Eck, N.J. (2020). Intermediacy of publications. Royal Society Open Science, 7(1), 190207. (paper)
• Waltman, L., Boyack, K.W., Colavizza, G., & Van Eck, N.J. (2020). A principled methodology for comparing relatedness measures for clustering publications. Quantitative Science Studies, 1(2), 691-713. (paper)
• Traag, V.A., & Waltman, L. (2019). Systematic analysis of agreement between metrics and peer review in the UK REF, e29. Palgrave Communications, 5. (paper)
• Traag, V.A., Waltman, L., & Van Eck, N.J. (2019). From Louvain to Leiden: guaranteeing well-connected communities, e5233. Scientific Reports, 9. (paper)
• Wouters, P., Sugimoto, C., Larivière, V., McVeigh, M.E., Pulverer, B., De Rijcke, S., & Waltman, L. (2019). Rethinking impact factors: Better ways to judge a journal (comment). Nature, 569, 621-623. (paper)
• Boyack, K.W., Van Eck, N.J., Colavizza, G., & Waltman, L. (2018). Characterizing in-text citations in scientific articles: A large-scale analysis. Journal of Informetrics, 12(1), 59-73. (paper)
• Colavizza, G., Boyack, K.W., Van Eck, N.J., & Waltman, L. (2018). The Closer the Better: Similarity of publication pairs at different co-citation levels. Journal of the Association for Information Science and Technology, 69(4), 600-609. (paper)
• Van de Laar, L., De Kruif, T., Waltman, L., Meijer, I., Gupta, A., & Hagenaars, N. (2018). Improving the evaluation of worldwide biomedical research output: classification method and standardised bibliometric indicators by disease. BMJ Open, 8(6), e020818. (paper)
• Van Eck, N.J., & Waltman, L. (2018). Analyzing the activities of visitors of the Leiden Ranking website. Journal of Data and Information Science, 3(3), 81-98. (paper)
• Boyack, K.W., Glänzel, W., Gläser, J., Havemann, F., Scharnhorst, A., Thijs, B., Van Eck, N.J., Van Velden, T., & Waltman, L. (2017). Topic identification challenge. Scientometrics, 111(2), 1223-1224. (paper)
• Van Eck, N.J., & Waltman, L. (2017). Citation-based clustering of publications using CitNetExplorer and VOSviewer. Scientometrics, 111(2), 1053-1070. (paper)
• Waltman, L. (2017). Special section on performance-based research funding systems. Editorial. Journal of Informetrics, 11(3), 904-904. (paper)
• Waltman, L., & Traag, V.A. (2017). Impact factors: Is the Nature Index at odds with DORA? (Correspondence). Nature, 545(7655), 412-412. (paper)
• Chorus, C., & Waltman, L. (2016). A Large-Scale Analysis of Impact Factor Biased Journal Self-Citations. PLoS ONE, 11(8), e0161021. (paper)
• Perianes-Rodriguez, A., Waltman, L., & Van Eck, N.J. (2016). Constructing bibliometric networks: A comparison between full and fractional counting. Journal of Informetrics, 10(4), 1178-1195. (paper)
• Subelj, L., Van Eck, N.J., & Waltman, L. (2016). Clustering scientific publications based on citation relations: A systematic comparison of different methods. PLoS ONE, 11(4), e0154404. (paper)
• Waltman, L. (2016). A review of the literature on citation impact indicators. Journal of Informetrics, 10(2), 365-391. (paper)
• Waltman, L. (2016). Conceptual difficulties in the use of statistical inference in citation analysis. Journal of Informetrics, 10(4), 1249-1252. (paper)
• Waltman, L. (2016). Special section on size-independent indicators in citation analysis. Editorial. Journal of Informetrics, 10(2), 645-645. (paper)
• Waltman, L. (2016). Special section on statistical inference in citation analysis. Editorial. Journal of Informetrics, 10(4), 1224-1224. (paper)
• Waltman, L., Van Eck, N.J., Visser, M.S., & Wouters, P. (2016). The elephant in the room: The problem of quantifying productivity in evaluative scientometrics. Journal of Informetrics, 10(2), 671-674. (paper)
• Wang, Q., & Waltman, L. (2016). Large-scale analysis of the accuracy of the journal classification systems of Web of Science and Scopus. Journal of Informetrics, 10(2), 347-364. (paper)
• De Groot, C.J.M., Van Leeuwen, T.N., Mol, B.J., & Waltman, L. (2015). A longitudinal analysis of publications on maternal mortality. Paediatric and Perinatal Epidemiology, 29(6), 481-489. (paper)
• Hicks, D., Wouters, P., Waltman, L., De Rijcke, S., & Rafols, I. (2015). The Leiden Manifesto for research metrics. Nature, 520(7548), 429-431. (paper)
• Ruiz-Castillo, J., & Waltman, L. (2015). Field-normalized citation impact indicators using algorithmically constructed classification systems of science. Journal of Informetrics, 9(1), 102-117. (paper)
• Stegehuis, C., Litvak, N., & Waltman, L. (2015). Predicting the long-term citation impact of recent publications. Journal of Informetrics, 9(3), 642-657. (paper)
• Waltman, L., & Van Eck, N.J. (2015). Field-normalized citation impact indicators and the choice of an appropriate counting method. Journal of Informetrics, 9(4), 872-894. (paper)
• Ahlgren, P., & Waltman, L. (2014). The correlation between citation-based and expert-based assessments of publication channels: SNIP and SJR vs. Norwegian quality assessments. Journal of Informetrics, 8(4), 985-996. doi:10.1016/j.joi.2014.09.010 (paper)
• Rodrigues, S.P., Van Eck, N.J., Waltman, L., & Jansen, F.W. (2014). Mapping patient safety: A large-scale literature review using bibliometric visualisation techniques. BMJ Open, 4(3), e004468. doi:10.1136/bmjopen-2013-004468 (paper)
• Van Eck, N.J., & Waltman, L. (2014). CitNetExplorer: A new software tool for analyzing and visualizing citation networks. Journal of Informetrics, 8(4), 802-823. doi:10.1016/j.joi.2014.07.006 (paper)
• Waltman, L., & Costas, R. (2014). F1000 Recommendations as a potential new data source for research evaluation: a comparison with citations. Journal of the Association for Information Science and Technology, 65(3), 433-445. doi:10.1002/asi.23040 (paper)
• Waltman, L., Van Raan, A.F.J., & Smart, S. (2014). Exploring the relationship between the engineering and physical sciences and the health and life sciences by advanced bibliometric methods. PLoS ONE, 9(10), e111530. (paper)
• Van Eck, N.J., Waltman, L., Van Raan, A.F.J., Klautz, R.J.M., & Peul, W.C. (2013). Citation analysis may severely underestimate the impact of clinical research as compared to basic research. PLoS ONE, 8(4), e62395. doi:10.1371/journal.pone.0062395 (paper)
• Waltman, L., & Schreiber, M. (2013). On the calculation of percentile-based bibliometric indicators. Journal of the American Society for Information Science and Technology, 64(2), 372-379. doi:10.1002/asi.22775 (paper)
• Waltman, L., & Van Eck, N.J. (2013). A smart local moving algorithm for large-scale modularity-based community detection. The European Physical Journal B, 86(11), e471. doi:10.1140/epjb/e2013-40829-0 (paper)
• Waltman, L., & Van Eck, N.J. (2013). A systematic empirical comparison of different approaches for normalizing citation impact indicators. Journal of Informetrics, 7(4), 833-849. doi:10.1016/j.joi.2013.08.002 (paper)
• Waltman, L., & Van Eck, N.J. (2013). Source normalized indicators of citation impact: an overview of different approaches and an empirical comparison. Scientometrics, 96(3), 699-716. doi:10.1007/s11192-012-0913-4 (paper)
• Waltman, L., Van Eck, N.J., & Wouters, P. (2013). Counting publications and citations: Is more always better? Journal of Informetrics, 7(3), 635-641. doi:10.1016/j.joi.2013.04.001 (paper)
• Waltman, L., Van Eck, N.J., Dekker, R., & Kaymak, U. (2013). An evolutionary model of price competition among spatially distributed firms. Computational Economics, 42(4), 373-391. doi:10.1007/s10614-012-9358-3 (paper)
• Waltman, L., Van Eck, N.J., Van Leeuwen, T.N., & Visser, M.S. (2013). Some modifications to the SNIP journal impact indicator. Journal of Informetrics, 7(2), 272-285. doi:10.1016/j.joi.2012.11.011 (paper)
• Waltman, L. (2012). An empirical analysis of the use of alphabetical authorship in scientific publishing. Journal of Informetrics, 6(4), 700-711. doi:10.1016/j.joi.2012.07.008 (paper)
• Waltman, L., & Van Eck, N.J. (2012). A mathematical analysis of the long-run behavior of genetic algorithms for social modeling. Soft Computing, 16(6), 1071-1089. doi:10.1007/s00500-012-0804-x (paper)
• Waltman, L., & Van Eck, N.J. (2012). A new methodology for constructing a publication-level classification system of science. Journal of the American Society for Information Science and Technology, 63(12), 2378-2392. doi:10.1002/asi.22748 (paper)
• Waltman, L., & Van Eck, N.J. (2012). The Inconsistency of the h-index. Journal of the American Society for Information Science and Technology, 63(2), 406-415. doi:10.1002/asi.21678 (paper)
• Waltman, L., Calero-Medina, C.M., Kosten, M.J.F., Noyons, E.C.M., Tijssen, R.J.W., Van Eck, N.J., Van Leeuwen, T.N., Van Raan, A.F.J., Visser, M.S., & Wouters, P. (2012). The Leiden Ranking 2011/2012: Data collection, indicators, and interpretation. Journal of the American Society for Information Science and Technology, 63(12), 2419-2432. doi:10.1002/asi.22708 (paper)
• Waltman, L., Costas, R., & Van Eck, N.J. (2012). Some limitations of the h Index: a commentary on Ruscio and colleagues' analysis of bibliometric indices. Measurement: Interdisciplinary Research and Perspectives, 10(3), 172-175. doi:10.1080/15366367.2012.716260 (paper)
• Waltman, L., Van Eck, N.J., & Van Raan, A.F.J. (2012). Universality of citation distributions revisited. Journal of the American Society for Information Science and Technology, 63(1), 72-77. doi:10.1002/asi.21671 (paper)
• Bornmann, L., & Waltman, L. (2011). The detection of "hot regions" in the geography of science-A visualization approach by using density maps. Journal of Informetrics, 5(4), 547-553. doi:10.1016/j.joi.2011.04.006 (paper)
• Egghe, L., & Waltman, L. (2011). Relations between the shape of a size-frequency distribution and the shape of a rank-frequency distribution. Information Processing & Management, 47(2), 238-245. doi:10.1016/j.ipm.2010.03.009 (paper)
• Tijssen, R.J.W., Waltman, L., & Van Eck, N.J. (2011). Collaborations span 1,553 kilometres. , 473(7346), 154-154. doi:10.1038/473154a (paper)
• Van Eck, N.J., & Waltman, L. (2011). Text mining and visualization using VOSviewer. ISSI Newsletter, 7(3), 50-54.
• Waltman, L., Tijssen, R.J.W., & Van Eck, N.J. (2011). Globalisation of science in kilometres. Journal of Informetrics, 5(4), 574-582. doi:10.1016/j.joi.2011.05.003 (paper)
• Waltman, L., Van Eck, N.J., & Dekker, R. (2011). Economic modeling using evolutionary algorithms: the effect of a binary encoding of strategies. Journal of Evolutionary Economics, 21(5), 737-756. doi:10.1007/s00191-010-0177-1 (paper)
• Waltman, L., Van Eck, N.J., & Yan, E. (2011). A recursive field-normalized bibliometric performance indicator: an application to the field of library and information science. Scientometrics, 89(1), 301-314. doi:10.1007/s11192-011-0449-z (paper)
• Waltman, L., Van Eck, N.J., Van Leeuwen, T.N., Visser, M.S., & Van Raan, A.F.J. (2011). On the correlation between bibliometric indicators and peer review: Reply to Opthof and Leydesdorff. Scientometrics, 88(3), 1017-1022. (paper)
• Waltman, L., Van Eck, N.J., Van Leeuwen, T.N., Visser, M.S., & Van Raan, A.F.J. (2011). Towards a new crown indicator: An empirical analysis. Scientometrics, 87(3), 467-481. (paper)
• Waltman, L., Van Eck, N.J., Van Leeuwen, T.N., Visser, M.S., & Van Raan, A.F.J. (2011). Towards a new crown indicator: Some theoretical considerations. Journal of Informetrics, 5(1), 37-47. doi:10.1016/j.joi.2010.08.001 (paper)
• Van Eck, N.J., & Waltman, L. (2010). Software survey: VOSviewer, a computer program for bibliometric mapping. Scientometrics, 84(2), 523-538. doi:10.1007/s11192-009-0146-3 (paper)
• Van Eck, N.J., Waltman, L., Dekker, R., & Van den Berg, J. (2010). A comparison of two techniques for bibliometric mapping: Multidimensional scaling and VOS. Journal of the American Society for Information Science and Technology, 61(12), 2405-2416. doi:10.1002/asi.21421 (paper)
• Van Eck, N.J., Waltman, L., Noyons, E.C.M., & Buter, R.K. (2010). Automatic term identification for bibliometric mapping. Scientometrics, 82(3), 581-596. doi:10.1007/s11192-010-0173-0 (paper)
• Van Raan, A.F.J., Van Leeuwen, T.N., Visser, M.S., Van Eck, N.J., & Waltman, L. (2010). Rivals for the crown: Reply to Opthof and Leydesdorff. Journal of Informetrics, 4(3), 431-435. doi:10.1016/j.joi.2010.03.008 (paper)
• Waltman, L., & Van Eck, N.J. (2010). The relation between Eigenfactor, audience factor, and influence weight. Journal of the American Society for Information Science and Technology, 61(7), 1476-1486. doi:10.1002/asi.21354 (paper)
• Waltman, L., Van Eck, N.J., & Noyons, E.C.M. (2010). A unified approach to mapping and clustering of bibliometric networks. Journal of Informetrics, 4(4), 629-635. doi:10.1016/j.joi.2010.07.002 (paper)
• Van Eck, N.J., & Waltman, L. (2009). How to Normalize Cooccurrence Data? An Analysis of Some Well-Known Similarity Measures. Journal of the American Society for Information Science and Technology, 60(8), 1635-1651. doi:10.1002/asi.21075 (paper)
• Van Eck, N.J., & Waltman, L. (2009). On the proper understanding of the limiting behavior of generalizations of the h- and g-indices. Journal of Informetrics, 3(4). doi:10.1016/j.joi.2009.02.002 (paper)
• Waltman, L., & Van Eck, N.J. (2009). A simple alternative to the h-index. ISSI Newsletter, 5(3), 46-48.
• Waltman, L., & Van Eck, N.J. (2009). Robust Evolutionary Algorithm Design for Socio-Economic Simulation: Some Comments. Computational Economics, 33(1), 103-105. doi:10.1007/s10614-008-9148-0 (paper)
• Waltman, L., & Van Eck, N.J. (2009). Some comments on Egghe's derivation of the impact factor distribution. Journal of Informetrics, 3(4), 363-366. doi:10.1016/j.joi.2009.05.004 (paper)
• Van Eck, N.J., & Waltman, L. (2008). Appropriate similarity measures for author co-citation analysis. Journal of the American Society for Information Science and Technology, 59(10), 1653-1661. doi:10.1002/asi.20872 (paper)
• Van Eck, N.J., & Waltman, L. (2008). Generalizing the h- and g- indices. Journal of Informetrics, 2(4), 263-271. doi:10.1016/j.joi.2008.09.004 (paper)
• Waltman, L., & Kaymak, U. (2008). Q-learning agents in a Cournot oligopoly model. Journal of Economic Dynamics & Control, 32(10), 3275-3293. doi:10.1016/j.jedc.2008.01.003 (paper)
• Waltman, L., & Van Eck, N.J. (2008). Some comments on the journal weighted impact factor proposed by Habibzadeh and Yadollahie. Journal of Informetrics, 2(4), 369-372. doi:10.1016/j.joi.2008.06.003 (paper)
• Van Eck, N.J., & Waltman, L. (2007). Bibliometric mapping of the computational intelligence field. International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems, 15(5), 625-645. doi:10.1142/S0218488507004911 (paper)
• Waltman, L., & Van Eck, N.J. (2007). Some comments on the question whether co-occurrence data should be normalized. Journal of the American Society for Information Science and Technology, 58(11), 1701-1703. doi:10.1002/asi.20647 (paper)
• Van Eck, N.J., Waltman, L., Van den Berg, J., & Kaymak, U. (2006). Visualizing the computational intelligence field. IEEE Computational Intelligence Magazine, 1(4), 6-10. doi:10.1109/MCI.2006.329702 (paper)

Conference publications (34)

• Van Eck, N.J., & Waltman, L. (2021). Crossref as a source of open bibliographic metadata. In W. Glänzel, S. Heeffer, P.-S. Chi, & R. Rousseau (Eds.), Proceedings of the 18th International Conference of the International Society for Scientometrics and Informetrics (pp. 1169-1174). (paper)
• Bascur, J.P., Verberne, S., Van Eck, N.J., & Waltman, L. (2020). Browsing citation clusters for academic literature search: a simulation study with systematic reviews. In G. Cabanac, I. Frommholz, & P. Mayr (Eds.), Proceedings of the 10th International Workshop on Bibliometric-enhanced Information Retrieval (pp. 53-65). (paper)
• Bascur, J.P., Van Eck, N.J., & Waltman, L. (2019). An interactive visual tool for scientific literature search: Proposal and algorithmic specification. In G. Cabanac, I. Frommholz, & P. Mayr (Eds.), Proceedings of the 8th International Workshop on Bibliometric-enhanced Information Retrieval (pp. 76-87). (paper)
• Lamers, W.S., Van Eck, N.J., & Waltman, L. (2019). Variations in citation practices across the scientific landscape: Analysis based on a large full-text corpus. In Proceedings of the 17th International Conference of the International Society for Scientometrics and Informetrics (pp. 2121-2132).
• Murray, D.S., Lamers, W.S., Boyack, K.W., Larivière, V., Sugimoto, C., Van Eck, N.J., & Waltman, L. (2019). Measuring disagreement in science. In Proceedings of the 17th International Conference of the International Society for Scientometrics and Informetrics (pp. 2370-2375).
• Subelj, L., Waltman, L., Traag, V.A., & Van Eck, N.J. (2019). Intermediacy of publications. In Proceedings of the 17th International Conference of the International Society for Scientometrics and Informetrics (pp. 1288-1300).
• Visser, M.S., Van Eck, N.J., & Waltman, L. (2019). Large-scale comparison of bibliographic data sources: Web of Science, Scopus, Dimensions, and Crossref. In Proceedings of the 17th International Conference of the International Society for Scientometrics and Informetrics (pp. 2358-2369).
• Lamers, W.S., Van Eck, N.J., Waltman, L., & Hoos, H.H. (2018). Patterns in citation context: The case of the field of scientometrics. In Proceedings of the 23rd International Conference on Science and Technology Indicators (pp. 1114-1122). (paper)
• Van Eck, N.J., & Waltman, L. (2018). Analyzing the activities of visitors of the Leiden Ranking website. In Proceedings of the 23rd International Conference on Science and Technology Indicators (pp. 857-867). (paper)
• Boyack, K.W., Van Eck, N.J., Colavizza, G., & Waltman, L. (2017). Reference behavior in the full text of scientific articles: A large-scale analysis. In Proceedings of the 16th International Conference of the International Society for Scientometrics and Informetrics (pp. 787-798).
• Colavizza, G., Boyack, K.W., Van Eck, N.J., & Waltman, L. (2017). Exploring the similarity of articles co-cited at different levels. In Proceedings of the 16th International Conference of the International Society for Scientometrics and Informetrics (pp. 549-560).
• Van Eck, N.J., & Waltman, L. (2017). Accuracy of citation data in Web of Science and Scopus. In Proceedings of the 16th International Conference of the International Society for Scientometrics and Informetrics (pp. 1087-1092).
• Van Eck, N.J., & Waltman, L. (2017). Using full-text data to create improved term maps. In Proceedings of the 16th International Conference of the International Society for Scientometrics and Informetrics (pp. 1136-1141).
• Waltman, L., Boyack, K.W., Colavizza, G., & Van Eck, N.J. (2017). A principled methodology for comparing relatedness measures for clustering publications. In Proceedings of the 16th International Conference of the International Society for Scientometrics and Informetrics (pp. 691-702).
• Waltman, L., & Van Eck, N.J. (2016). The need for contextualized scientometric analysis: An opinion paper. In Proceedings of the 21st International Conference on Science and Technology Indicators (pp. 541-549). (paper)
• Waltman, L., & Van Eck, N.J. (2015). Field-normalized citation impact indicators and the choice of an appropriate counting method. In Proceedings of the 15th International Conference of the International Society for Scientometrics and Informetrics (pp. 328-339). (paper)
• Van Eck, N.J., & Waltman, L. (2014). CitNetExplorer: A new software tool for analyzing and visualizing citation networks. In Proceedings of the 19th International Conference on Science and Technology Indicators (pp. 181-192).
• Costas, R., Calero-Medina, C.M., Waltman, L., & Wouters, P. (2013). The relationship between the performance of editorial board members and the impact of scientific journals : an exploratory analysis. In Proceedings of 18th International Conference on Science and Technology Indicators (pp. 87-95).
• Waltman, L., & Van Eck, N.J. (2013). A systematic empirical comparison of different approaches for normalizing citation impact indicators. In Proceedings of the 14th International Conference of the International Society for Scientometrics and Informetrics (pp. 1649-1664).
• Waltman, L., Wouters, P., & Van Eck, N.J. (2013). Counting publications and citations: Is more always better? 14th International Conference of the International Society for Scientometrics and Informetrics, Vienna. In Proceedings of the 14th International Conference of the International Society for Scientometrics and Informetrics (pp. 455-467).
• Tijssen, R.J.W., Waltman, L., & Van Eck, N.J. (2012). Research collaboration and the expanding science grid: Measuring globalization processes worldwide. In Proceedings of the 17th International Conference on Science and Technology Indicators (pp. 779-790).
• Waltman, L., & Van Eck, N.J. (2012). Constructing a publication-level classification system of science. In Proceedings of the 17th International Conference on Science and Technology Indicators (pp. 803-814).
• Waltman, L., Calero-Medina, C.M., Kosten, M.J.F., Noyons, E.C.M., Tijssen, R.J.W., Van Eck, N.J., Van Leeuwen, T.N., Van Raan, A.F.J., Visser, M.S., & Wouters, P. (2012). The Leiden Ranking 2011/2012: Data collection, indicators, and interpretation. In Proceedings of the 17th International Conference on Science and Technology Indicators (pp. 791-802).
• Van Eck, N.J., Tijssen, R.J.W., & Waltman, L. (2011). Globalization of public-private research in worldwide science: co-publication trends and geographical distances between research partners . In Proceedings of the 2011 Atlanta Conference on Science and Innovation Policy.
• Van Eck, N.J., Waltman, L., & Tijssen, R.J.W. (2011). Globalization of science: Geographical distance measurements of research collaboration. In Proceedings of the 13th International Conference of the International Society for Scientometrics and Informetrics (pp. 181-186).
• Waltman, L., & Bornmann, L. (2011). The detection of "hot regions" in the geography of science - A visualization approach by using density maps. The13th Conference of the International Society for Scientometrics and Informetrics. In Proceedings of the 13th International Conference of the International Society for Scientometrics and Informetrics (pp. 1076-1078).
• Van Eck, N.J., & Waltman, L. (2009). VOSviewer: A computer program for bibliometric mapping . In Proceedings of the 12th International Conference of the International Society for Scientometrics and Informetrics.
• Van Eck, N.J., & Waltman, L. (2009). VOSviewer: A computer program for bibliometric mapping. In Proceedings of the 12th International Conference of the International Society for Scientometrics and Informetrics (pp. 886-897).
• Waltman, L., & Van Eck, N.J. (2009). A Taxonomy of Bibliometric Performance Indicators Based on the Property of Consistency. In Proceedings of the 12th International Conference of the International Society for Scientometrics and Informetrics (pp. 1002-1003).
• Waltman, L., & Kaymak, U. (2007). A theoretical analysis of cooperative behaviorin multi-agent Q-learning. In Proceedings of the 2007 IEEE International Symposium on Approximate Dynamic Programming and Reinforcement Learning (pp. 84-91). doi:10.1109/ADPRL.2007.368173 (paper)
• Van Eck, N.J., Waltman, L., Van den Berg, J., & Kaymak, U. (2006). Visualizing the WCCI 2006 knowledge domain. In Proceedings of the 2006 IEEE International Conference on Fuzzy Systems (pp. 1671-1678). doi:10.1109/FUZZY.2006.1681931 (paper)
• Van Eck, N.J., Waltman, L., & Van den Berg, J. (2005). A novel algorithm for visualizing concept associations. In Proceedings of the 16th International Workshop on Database and Expert Systems Applications (pp. 405-409). doi:10.1109/DEXA.2005.23 (paper)
• Waltman, L., Kaymak, U., & Van den Berg, J. (2005). Maximum likelihood parameter estimation in probabilistic fuzzy classifiers. In Proceedings of the 2005 IEEE International Conference on Fuzzy Systems (pp. 1098-1103). doi:10.1109/FUZZY.2005.1452548 (paper)
• Van den Berg, J., Van Eck, N.J., Waltman, L., & Kaymak, U. (2004). A VICORE architecture for intelligent knowledge management. In Proceedings of the KDNet Symposium on Knowledge-Based Services for the Public Sector (pp. 63-74).

Book chapters (3)

• Waltman, L., & Van Eck, N.J. (2019). Field normalization of scientometric indicators. In W. Glänzel, H.F. Moed, U. Schmoch, & M. Thelwall (Eds.), Springer Handbook of Science and Technology Indicators (pp. 281-300). Springer. doi:10.1007/978-3-030-02511-3_11 (paper)
• Van Eck, N.J., & Waltman, L. (2014). Visualizing bibliometric networks. In Y. Ding, R. Rousseau, & D. Wolfram (Eds.), Measuring Scholarly Impact (pp. 285-320). Springer International Publishing. doi:10.1007/978-3-319-10377-8_13 (paper)
• Van Eck, N.J., & Waltman, L. (2007). VOS: A new method for visualizing similarities between objects. In R. Decker, & H.J. Lenz (Eds.), Studies in Classification, Data Analysis, and Knowledge Organization (pp. 299-306). Springer. doi:10.1007/978-3-540-70981-7_34 (paper)