Citation analysis at: http://scholar.google.com/citations?hl=en&user=jDmcdsUAAAAJ
Last updated February 2020
- Valdez Danny, ten Thij Marijn, Bathina Krishna, Rutter Lauren A, Bollen Johan (2020) Social-media insights into US mental health amid the COVID-19 global pandemic: a longitudinal analysis of publicly available Twitter data. Journal of Medical Internet Research 22(12):e21418, DOI: 10.2196/21418
- Marijn ten Thij, Krishna Bathina, Lauren A. Rutter, Lorenzo Lorenzo‑Luaces, Ingrid A. van de Leemput, Marten Scheffer & Johan Bollen (2020) Depression alters the circadian pattern of online activity Scientific Reports:10(17272), https://rdcu.be/b8vzU & doi.org/10.1038/s41598-020-74314-3
- Marijn ten Thij, Lauren Rutter, Lorenzo Lorenzo-Luaces and Johan Bollen (2020). Revealing the complex comorbidity structure of internalizing disorders through hypergraph models. Regular presentation, accepted at COMPLEX NETWORKS 2020, Madrid, Spain
- Rutter, L. A., Bathina, K., ten Thij, M., Lorenzo-Luaces, L., and Bollen, J. (2020, November). Distorted thinking online: evidence for cognitive distortions in depressed twitter users. In Rutter, L.A. (Chair), Social media and mental health: Exploring cognitive and behavioral mechanisms using diverse methodologies. Symposium accepted at the 54rd Annual Convention of the Association of Behavioral and Cognitive Therapies, Philadelphia, PA.
- Lorenzo-Luaces, L., ten Thij, M., Rutter, L. A., and Bollen, J. (2020, November). Online social media activity shows differences in the circadian rhythm of depressed vs. non-depressed Twitter users. Symposium accepted at the 54rd Annual Convention of the Association of Behavioral and Cognitive Therapies, Philadelphia, PA.
- Rion Brattig Correia, Ian B. Wood, Johan Bollen, and Luis M Rocha (2020).
Mining social media data for biomedical signals and health-related behavior
Annual Review of Biomedical Data Sciencei volume 3:1.
Krishna C. Bathina, Marijn ten Thij, Lorenzo Lorenzo-Luaces, Lauren A. Rutter, and Johan Bollen* (2020)
Depressed individuals express more distorted thinking on social media (preprint: arXiv:2002.02800)
Marijn ten Thij, Johan Bollen, and Luis M. Rocha (2020)
Detecting eigenmoods in individual human emotions, COMPLEX NETWORKS 2019, Lisbon, Portugal (extended abstract)
Rui Fan, Onur Varol, Ali Varamesh, Alexander Barron, Ingrid A. van de Leemput, Marten Scheffer & Johan Bollen (2019)
The minute-scale dynamics of online emotions reveal the effects of affect labeling,
Nature Human Behaviour, volume 3:92–100, doi: 10.1038/s41562-018-0490-5
Johan Bollen, Stephen R. Carpenter, Jane Lubchenco and Marten Scheffer (2019)
Rethinking resource allocation in science , Ecology and Society, 24(3):29 (invited manuscript)
Johan Bollen (2018) Who would you share your funding with?
Nature:560(143) August (https://www.nature.com/articles/d41586-018-05887-3, doi: 10.1038/d41586-018-05887-3)
Rui Fan, Ali Varamesh, Onur Varol, Alexander Barron, Ingrid van de Leemput,
Marten Scheffer, and Johan Bollen (2018)
Does putting your emotions into words make you feel better?
Measuring the minute-scale dynamics of emotions from online data.
Johan Bollen and Bruno Goncalves (2018)
Network Happiness: How Online Social Interactions Relate to Our Well Being
In Complex Spreading Phenomena in Social Systems -- Influence and Contagion in Real-World Social Networks.
Eds: Sune Lehmann and Yong-Yeol Ahn. Springer ISBN 978-3-319-77332-2
Erick Elejalde, Leo Ferres, Eelco Herder, and Johan Bollen (2018)
Quantifying the ecological diversity and health of online news.
Journal of Computational Science:27:218-226
Jorge Bahamonde, Johan Bollen, Erick Elejalde, Leo Ferres, and Barbara Poblete (2018)
Power structure in Chilean news media.
PloS ONE:13(6), e0197150
Ian Wood, Pedro Varela, Johan Bollen, Luis Rocha, and Joana Gonçalves-Sá (2017)
Human Sexual Cycles are Driven by Culture and Match Collective Moods.
Scientific Reports: 7(#17973)
F Radicchi, A Weissman, J Bollen (2017)
Quantifying perceived impact of scientific publications.
Journal of Informetrics 11(3):704-712, August
- Johan Bollen*, Bruno Gonçalves, Ingrid van de Leemput and Guangchen Ruan (2017)
The happiness paradox: your friends are happier than you
, EPJ Data Science 6(4),
N Rodriguez, J Bollen, YY Ahn (2016)
Collective dynamics of belief evolution under cognitive coherence and social conformity.
PLoS ONE 11(11)
X Liu, X Yu, Z Gao, T Xia, J Bollen (2016)
Comparing Community-based Information Adoption and Diffusion Across Different Microblogging Sites.
Proceedings of the 27th ACM Conference on Hypertext and Social Media:103-112
J Bollen, D Crandall, D Junk, Y Ding, K Börner (2016)
An efficient system to fund science: from proposal review to peer-to-peer distributions.
H Mao, X Shuai, YY Ahn, J Bollen (2015)
Quantifying socio-economic indicators in developing countries from mobile phone communication data: applications to Côte d’Ivoire.
EPJ Data Science 4(1):15
H Mao, S Counts, J Bollen (2015)
Quantifying the effects of online bullishness on international financial markets.
ECB Statistics Paper Series 9(17)
GL Ciampaglia, P Shiralkar, LM Rocha, J Bollen, F Menczer, A Flammini (2015)
Computational fact checking from knowledge networks.
PloS one 10(6):e0128193
X Dong, J Bollen (2015)
Computational models of consumer confidence from large-scale online attention data: crowd-sourcing econometrics.
PloS one 10 (3), e0120039
- J Bollen, D Crandall, D Junk, Y Ding, K Börner (2014)
Response:“Why we still need grant peer review”.
EMBO reports 15(5):467-467
J Bollen, D Crandall, D Junk, Y Ding, K Börner (2014)
From funding agencies to scientific agency.
EMBO reports 15(2):131-133
H Mao, P Gao, Wang Y, Bollen J (2014)
Automatic construction of financial semantic orientation lexicon from large-scale Chinese news corpus.
Institut Louis Bachelier, 20 (2):1-18
- Nathaniel Rodriguez, Johan Bollen and Yong-Yeol Ahn. Belief Polarization: Origins in Human Behavior
and Social Structure. Oral Presentation at COVENANT 2013 workshop at ECCS2013, September, Barcelona, Spain.
- Huina Mao, Xin Shuai, Yong-Yeol Ahn and Johan Bollen, Mobile Communications Reveal the Regional economy in Côte D’Ivoire. NetMob 2013, May 1-3, MIT (Cambridge, MA).
- Joseph DiGrazia, Karissa McKelvey, Johan Bollen, and Fabio Rojas, More Tweets, More Votes:
Social Media as a Quantitative Indicator of Political Behavior. Subm. PLoS ONE, under review
- Johan Bollen, David Crandall, Damion Junk, Ying Ding, and Katy Boerner, Collective allocation of science funding: from funding agencies to scientific agency,
- Xin Shuai, Zhuoren Jiang, Xiaozhong Liu and Johan Bollen, A Comparative Study of Academic impact and Wikipedia Ranking,
Proceedings of the Joint Conference on Digital Libraries 2013, Indianapolis, IN.
- He, B., Ding, Y., Tang, J., Reguramalingam, V., & Bollen, J. Mining diversity subgraph in multidisciplinary scientific collaboration networks: A meso perspective. Journal of Informetrics, Volume 7, Issue 1, January 2013, Pages 117–128
- Jasleen Kaur and Johan Bollen. Structural Patterns in Online Usage. In ACM Web Science Conference - Altmetrics 12 Workshop (presentation only), June 2012, Chicago, IL - http://altmetrics.org/altmetrics12/program/
- Shuai X, Pepe A, Bollen J (2012) How the Scientific Community Reacts to Newly Submitted Preprints: Article Downloads, Twitter Mentions, and Citations. PLoS ONE 7(11): e47523. doi:10.1371/journal.pone.0047523
- Daifeng Li, Ying Ding, Xin Shuai, Johan Bollen, Jie Tang, Shanshan Chen, Jiayi Zhu, and Guilherme Rocha. Adding Community and Dynamic to Topic Models. Journal of Informetrics, 6(2): 237-253, 2012
Xin Shuai, Xiaozhong Liu, and Johan Bollen. Improving News Ranking by Community Tweets. In WWW 2012 – MSND'12 Workshop, pp. 1227-1232. France, Lyon
- Huina Mao, Scott Counts and Johan Bollen. Computational Economic and Finance Gauges: Polls, Search, and Twitter. Meeting of the National Bureau of Economic Research - Behavioral Finance Meeting, Stanford, CA, November 5th, 2011
- Johan Bollen and Huina Mao. Twitter Mood as a Stock Market Predictor. IEEE Computer, 44(10): 91-94, October 2011.
- Johan Bollen, Bruno Gonçalves, Guangchen Ruan & Huina Mao. Happiness is assortative in online social networks. Artificial Life, Summer - 17(3), 237-251 (2011) (arxiv:1103.0784, doi:10.1162/artl_a_00034)
- Johan Bollen, Alberto Pepe, and Huina Mao. Modeling public mood and emotion: Twitter sentiment and socio-economic phenomena. ICWSM11, Barcelona, Spain, July 2011 (arXiv: 0911.1583) - poster.
Johan Bollen, Huina Mao, and Xiao-Jun Zeng. Twitter mood predicts the stock market. Journal of Computational Science, 2(1), March 2011, Pages 1-8, doi:10.1016/j.jocs.2010.12.007, arxiv: abs/1010.3003. (featured on CNBC, CNN International and Bloomberg News!)
- Johan Bollen, Herbert Van de Sompel, Aric Hagberg and Ryan Chute. A Principal Component Analysis of 39 Scientific Impact Measures. PLoS ONE, June 2009. URL: http://dx.plos.org/10.1371/journal.pone.0006022.
- Bollen J, Van de Sompel H, Hagberg A, Bettencourt L, Chute R, et al. (2009) Clickstream Data Yields High-Resolution Maps of Science. PLoS ONE 4(3): e4803. doi:10.1371/journal.pone.0004803
Marko A. Rodriguez, Johan Bollen, and Herbert Van de Sompel. Automatic Metadata Generation using Associative Networks. Transactions on Information Systems, Volume 27, Issue 2, February 2009.
- Marko A. Rodriguez and Johan Bollen. "An Algorithm to Determine Peer-Reviewers", Conference on Information and Knowledge Management (CIKM), in press, Napa Valley, California, ACM, LA-UR-06-2261, October 2008.
- Johan Bollen, Herbert Van de Sompel, Luda Balakireva and Ryan Chute. A ranking and exploration service based on large-scale usage data. JCDL 2008, Pittsburgh, PA, June 2008. (best poster award)
- Johan Bollen, Herbert Van de Sompel and Marko A. Rodriguez. Towards usage-based impact metrics: first results from the MESUR project, JCDL 2008, Pittsburgh, PA, June 2008. (arXiv:0804.3791v1, best paper finalist)
- Johan Bollen and Herbert Van de Sompel. MESUR: implications of usage-based evaluations of scholarly status for open repositories. Open Repositories, Southampton, UK, April, 2008.
- Alberto Pepe and Johan Bollen. Between conjecture and memento: shaping a collective emotional perception of the future. AAAI 2008 Spring Symposium on Emotion, Personality and Social Behavior, Stanford, March 26-28, 2008.
Johan Bollen and Herbert Van de Sompel. Usage Impact Factor: the effects of sample characteristics on usage-based impact metrics. Journal of the American Society for Information Science and technology, 59(1), January 2008, pages 001-014 (cs.DL/0610154).
- Rodriguez, M.A., Watkins, J.H., Bollen, J., Gershenson, C., Using RDF to Model the Structure and Process of Systems, International Conference on Complex Systems, Boston, Massachusetts, LAUR-07-5720, October 2007.
- Johan Bollen, Marko A. Rodriguez and Herbert Van de Sompel. MESUR: usage-based metrics of scholarly impact (poster). In Proceedings of the Joint Conference on Digital Libraries, Vancouver, June 2007
- Johan Bollen, Marko Rodriguez, Herbert Van de Sompel, Lyudmilla Balakireva, and Aric Hagberg, The Largest Scholarly Semantic Network...Ever (poster). In Proceedings of the 16th International World Wide Web conference, May 2007. - Note: Best Poster Award!
- Marko. A Rodrguez, Johan Bollen and Herbert Van de Sompel. A Practical Ontology for the Large-Scale Modeling of Scholarly Artifacts and their Usage, In Proceedings of the Joint Conference on Digital Libraries, Vancouver, June 2007
- Robert P Dellavalle, Lisa M Schilling, Marko A Rodriguez, Herbert Van de Sompel, and Johan Bollen. Refining Dermatology Journal Impact Factors Using PageRank. Journal of the American Academy of Dermatology, Volume 30(3), pages 1059-1083, August 2007.
- Steen Rasmussen, Diana Mangalagiu, Hans Ziock, Johan Bollen and Gordon Keating. Collective intelligence for decision support in very large stakeholder networks: The future US energy system. ALIFE 2007- IEEE Symposium on Artificial Life, April 2007.
- Ann Heylighen, Francis Heylighen, Johan Bollen and Mathias Casaer. Distributed (design) knowledge exchange. Artificial Intelligence & Society - Special issue on Mediated Communication in Action: a Social Intelligence Design Approach, in press, 2007.
- Marko. A. Rodriguez, J. Bollen, and Herbert Van de Sompel. Mapping the Bid Behavior of Conference Referees, Journal of Informetrics, 1(1), January 2007.
Marko A. Rodriguez, Daniel J. Steinbock, Jennifer H. Watkins, Carlos Gershenson, Johan Bollen, Victor Grey, and Brad deGraf. Smartocracy: Social networks for collective decision making. In Proceedings of the International Conference on Systems Science (HICSS), Hawaii, January 2007.
- Johan Bollen and Herbert Van de Sompel. An architecture for the aggregation and analysis of scholarly usage data. In Joint Conference on Digital Libraries (JCDL2006), pages 298–307, June 2006.
- Johan Bollen and Herbert Van de Sompel. Mapping the structure of science through usage. Scientometrics, 69(2), 2006 (DOI: 10.1007/s11192-006-0151-8).
- Johan Bollen, Michael L. Nelson, Gary Geisler, and Raquel Araujo. Usage derived recommendations for a video digital library. Journal of Network and Computer Applications, 30 (3), pp. 1059-1083, 2007. (doi:10.1016/j.jnca.2005.12.009).
- Johan Bollen, Marko A. Rodriguez, and Herbert Van de Sompel. Journal status. Scientometrics, 69(3), December 2006 (arxiv.org:cs.DL/0601030, DOI: 10.1007/s11192-006-0176-z)
- Frank McCown, Joan A. Smith, Michael L. Nelson, and Johan Bollen. Lazy preservation: Reconstructing websites by crawling the crawlers. In Eight ACM International Workshop on Web Information and Data Management (WIDM 2006), November 2006.
Marko A. Rodriguez, Johan Bollen, and Herbert Van de Sompel. An analysis of the bid behavior of the 2005 JCDL Program Committee (poster). In Joint Conference on Digital Libraries (JCDL2006), pages 352–352, June 2006.
- Johan Bollen, Herbert Van de Sompel, Joan Smith, and Rick Luce. Toward alternative metrics of journal impact: a comparison of download and citation data. Information Processing and Management, 41(6):1419–1440, 2005.
- Johan Bollen, Michael L. Nelson, Gary Geisler, and Raquel Araujo. Video recommendations for the Open Video Project (poster). In Proceedings of Joint Conference on Digital Libraries (JCDL05), page 369, June 2005.
- Johan Bollen, Michael L. Nelson, Giridhar Manepalli, Giridhar Nandigam, and Suchitra Manepalli. Trend analysis of the digital library community. D-Lib Magazine, 11(1), January 2005.
- Sheffan Chan, Frank McCown, Michael L. Nelson, and Johan Bollen. The availability and persistence of web references in D-Lib Magazine. In 5th International Workshop on Web Archiving and Digital Preservation (in conjunction with ECDL2005), September 2005.
- Xiaoming Liu, Johan Bollen, Michael L. Nelson, and Herbert Van de Sompel. Co-authorship networks in the digital library research community. Information Processing and Management, 41(6):1462–1480, December 2005.
- Thomas Lutkenhouse, Michael L. Nelson, and Johan Bollen. Distributed, real-time computation of community preferences. In Proceedings of the Sixteenth ACM Conference on Hypertext and Hypermedia HT05, pages 88–97, September 2005.
- Frank McCown, Johan Bollen, and Michael L. Nelson. Evaluation of the NSDL and Google for obtaining pedagogical resources. In Ninth European Conference on Research and Advanced Technology for Digital Libraries (ECDL2005), pages 344–355, September 2005.
- Michael L. Nelson and Johan Bollen. If you harvest arXiv.org, will they come? (poster). In Proceedings of Joint Conference on Digital Libraries (JCDL05), June 2005.
- Michael L. Nelson, Johan Bollen, Giridhar Manepalli, and Rabia Haq. Archive ingest and handling test: The Old Dominion University approach. D-Lib Magazine, 11(12), December 2005.
- Marko A. Rodriguez, Johan Bollen, and Herbert Van de Sompel. The convergence of the digital libraries and the peer review process. Journal of Information Science, 32:149–159, 2005.
Jewel Ward, Johan Bollen, J. Pearson, S. Chan, H. Chi, M. Chi, K. Guevara, H. Huang, G. Kim, M. Krivokon, B. H. Lee, P. Li., F. Muliawan, V. Nguyen, B. W. Boehm, A. W. Brown, E. Colbert, and A. Lamand M. Patel. Mining and analyzing digital archive usage data to support collection development decisions (poster). In Proceedings of Joint Conference on Digital Libraries (JCDL05), page 417, June 2005.
- Aravind Elango, Johan Bollen, and Michael Nelson. Dynamic linking of smart digital objects based on user navigation patterns. Technical Report cs.DL/0401029, arXiv, January 2004.
- Xiaoming Liu, Johan Bollen, Michael L. Nelson, Herbert Van de Sompel, Jeremy Hussell, Rick Luce, and Linn Marks. Toolkits for visualizing co-authorship graph. In Proceedings of the 2004 joint ACM/IEEE conference on Digital libraries, pages 404–404, Tuscon, AZ, 2004. (doi:10.1109/JCDL.2004.101)
- Michael L. Nelson, Johan Bollen, JoAnne R. Calhoun, and Calvin E. Mackey. User evaluation of the NASA Technical Report Server Recommendation Service. In 6th ACM International Workshop on Web Information and Data Management (WIDM 2004), pages 144–152, November 2004.
- Johan Bollen. Review of Development of Digital Libraries - An American Perspective by Deanna B. Marcum. Journal of Documentation, 59, 2003.
- Johan Bollen, Rick Luce, Somasekhar Vemulapalli, and Weining Xu. Usage analysis for the identification of research trends in digital libraries. D-Lib Magazine, 9(5), 2003.
- Johan Bollen, Rick Luce, Somesekhar Vemulapalli, and Weining Xu. Detecting research trends in digital library readership. In Proceedings of the Seventh European Conference on Digital Libraries (LNCS 2769), pages 24–28, Trondheim, Norway, August 18 2003. Springer-Verlag.
Aravind Elango, Michael Nelson, and Johan Bollen. Dynamic linking of smart digital objects based on user navigation patterns. In Bella Bose, S.N.Sivananthan, and A.Chitra, editors, Eleventh International Conference on Advanced Computing and Communications (ADCOM), Coimbatore, India, December 2003.
- Johan Bollen and Rick Luce. Evaluation of digital library impact and user communities by analysis of usage patterns. D-Lib Magazine, 8(6), 2002.
- Johan Bollen and Michael L. Nelson. Adaptive networks of smart objects. In Johan Bollen and Michael L. Nelson, editors, Proceedings of Workshop on Distributed Computing Architectures for Digital Libraries (ICPP2002), pages 487–496, Vancouver, B.C., Canada, August 18-21 2002. IEEE.
- Johan Bollen, Somasekhar Vemulapalli, and Weining Xu. Digital library evaluation by analysis of user retrieval patterns. In Maristella Agosti and Costantino Thanos, editors, Sixth European Conference on Research and Advanced Technology for Digital Libraries - LNCS, pages 432–448, Rome, Italy, September 2002. Springer Verlag.
Francis Heylighen and Johan Bollen. Hebbian algorithms for digital library recommendation systems. In Johan Bollen and Michael L. Nelson, editors, Proceedings of Workshop on Distributed Computing Architectures for Digital Libraries (ICPP2002), pages 439–447, Vancouver, B.C., Canada, August 18-21 2002. IEEE.
- 2001, ...
- Johan Bollen. A cognitive model of adaptive web design and navigation. PhD thesis, Vrije Universiteit Brussel, Brussels, Belgium, 2001.
- Mariella Di Giacomo, Dan Mahoney, Johan Bollen, Andres Monroy-Hernandez, and Cesar M. Ruiz Meraz. Mylibrary, a personalization service for digital library environments. In DELOS Workshop: Personalisation and Recommender Systems in Digital Libraries, Dublin, Ireland, June 2001.
- Johan Bollen. Group user models for personalized hyperlink recommendation. In LNCS 1892 - International Conference on Adaptive Hypermedia and Adaptive Web-based Systems (AH2000), pages 39–50, Trento, August 2000. Springer Verlag.
- Johan Bollen and Luis M. Rocha. An adaptive systems approach to the implementation and evaluation of digital library recommendation systems. In LNCS - Fourth European Conference on Research and Advanced Technology for Digital Libraries (ECDL2000), Lisbon, September 2000. Springer Verlag.
- Luis M. Rocha and Johan Bollen. Biologically motivated distributed designs for adaptive knowledge management. In I.Cohen and L. Segel, editors, Design Principles for the Immune System and other Distributed Autonomous Systems, pages 305–334. Oxford University Press, Oxford, 2000.
- Johan Bollen. Cognitive complexity vs. connectivity: efficiency analysis of hypertext networks. In Francis Heylighen, Johan Bollen, and Alex Riegler, editors, The Evolution of Complexity, pages 345–368. Kluwer Academic Publishers, Dordrecht, 1999.
- Johan Bollen, Herbert Van de Sompel, and Luis M. Rocha. Mining associative relations from website logs and their application to context-dependent retrieval using spreading activation. In Proceedings of the Workshop on Organizing Webspaces (ACM-DL99), Berkeley, California, 1999.
- Francis Heylighen, Johan Bollen, and Alex Riegler, editors. The Evolution of Complexity. Kluwer Academic Publishers, Dordrecht, 1999.
- Johan Bollen and Francis Heylighen. A system to restructure hypertext networks into valid user models. The New Review of Hypermedia and Multimedia, 4:189–213, 1998.
- Johan Bollen, Francis Heylighen, and Dirk van Rooy. Improving memetic evolution in hypertext and the WWW. In Proceedings of the 15th International Congress on Cybernetics, pages 449–454, Namur, 1998. International Association of Cybernetics.
- Paul Marsden and Johan Bollen. Help advertising evolve: clone consumber thought-patterns. AdMap, 34(3):37–39, 1998.
- Johan Bollen and Francis Heylighen. Dynamic and adaptive structuring of the world wide web based on user navigation patterns. In Proceedings of the Flexible Hypertext Workshop, pages 13–17, Sydney, 1997. Macquarie Computing Reports.
- Johan Bollen. Selfstructuring hypertext networks that learn to reflect the common semantics of their users: applications to the WWW. In Proceedings of the Annual Meeting of the Belgian Psychological Society, Brussels, 1996. Belgian Psychological Society.
- Johan Bollen and Francis Heylighen. Algorithms for the self-organization of distributed, multi-user networks. In R. Trappl, editor, Proceedings of the 13th European Meeting on Cybernetics and Systems Research, pages 911–917, Vienna, Austria, 1996. Austrian Society for Cybernetic Studies.
- Francis Heylighen and Johan Bollen. The world-wide web as a super-brain: from metaphor to model. In R. Trappl, editor, Cybernetics and Sstems '96, pages 917–925. Austrian Society for Cybernetic Studies, 1996.
- Johan Bollen. Adaptive hypertext networks that learn the common semantics of their users. In Proceedings of the 14th Int. Congress on Cybernetics, pages 251–255, Namur, 1995. International Association of Cybernetics.
- Johan Bollen. The principia cybernetica web: a knowledge base for systems research. International Federation for Systems Research Newsletter, 34, December 1994.