The main publication to cite when you use COPASI in your research is:
Hoops S., Sahle S., Gauges R., Lee C., Pahle J., Simus N., Singhal M., Xu L., Mendes P. and Kummer U. (2006). COPASI: a COmplex PAthway SImulator. Bioinformatics 22, 3067-74. Link | ISI Citations | Google Scholar Citations
Publications describing uses of COPASI in some detail:
Mendes, P., Hoops, S., Sahle, S., Gauges, R., Dada, J.O. and Kummer, U. (2009). Computational Modeling of Biochemical Networks Using COPASI. Methods in Molecular Biology, Humana Press. 500: 17-59. Link
Mendes, P., Messiha, H., Malys, N. and Hoops, S. (2009). Enzyme Kinetics and Computational Modeling for Systems Biology. Methods in Enzymology 467: 583-599. Link | ISI Citations | Google Scholar Citations
Sahle, S., Gauges, R. , Pahle, J., Simus, N., Kummer, U., Hoops, S., Lee, C., Singhal, M., Xu, L. and Mendes, P. (2006). Simulation of biochemical networks using COPASI: a complex pathway simulator. Proceedings of the 38th conference on Winter simulation. Monterey, California, Winter Simulation Conference. 1698-1706 Link
Research papers describing methods that are (or will be) used in COPASI:
Challenger, J.D., McKane, A.J. and Pahle, J. (2012). Multi-compartment linear noise approximation. J. Stat. Mech. P11010. Link
Pahle, J., Challenger, J.D., Mendes, P. and McKane, A.J. (2012). Biochemical fluctuations, optimisation and the linear noise approximation. BMC Systems Biology 6: 86. Link
Dada, J.O., Spasic, I., Paton, N.W. and Mendes, P. (2010). SBRML: a markup language for associating systems biology data with models. Bioinformatics 26: 932-938. Link
Surovtsova, I., Simus, N., Lorenz, T., König, A., Sahle, S. and Kummer, U. (2009). Accessible methods for the dynamic time-scale decomposition of biochemical systems.Bioinformatics 25: 2816-2823. Link
Pahle, J. (2009). Biochemical simulations: stochastic, approximate stochastic and hybrid approaches.Briefings in Bioinformatics 10: 53-64. Link | ISI Citations | Google Scholar Citations
Sahle, S. Mendes, P., Hoops, S. and Kummer, U. (2008). A new strategy for assessing sensitivities in biochemical models. Philosophical Transactions of the Royal Society A - Mathematical Physical and Engineering Sciences 366(1880): 3619-3631. Link | ISI Citations | Google Scholar Citations
Pahle, J. (2008). Stochastic simulation and analysis of biochemical networks. PhD Thesis, Humboldt-Universität zu Berlin Link | Google Scholar Citations
Kummer, U. (2007). Usage of Reaction Kinetics Data Stored in Databases - A Modeler's Point of View. In Silico Biology 7: 65-71. Link | Google Scholar Citations
Gauges, R., Rost, U., Sahle, S. and Wegner, K. (2006). A model diagram layout extension for SBML.Bioinformatics 22: 1879-85. Link | ISI Citations | Google Scholar Citations
Publications describing other software applications that use COPASI:
Kent E, Hoops S, Mendes P (2012). Condor-COPASI: High-Throughput Computing for Biochemical Networks. BMC Systems Biology 6:91 link
Dada, J.O. and Mendes, P. (2009). Design and Architecture of Web Services for Simulation of Biochemical Systems. Data Integration in the Life Sciences; Lecture Notes in Computer Science, Springer, Berlin / Heidelberg. 5647: 182-195. Link
Schulz, M., Bakker, B.M., Klipp, E. (2009) TIde: a software for the systematic scanning of drug targets in kinetic network modelsBMC Bioinformatics : 10. Link | Google Scholar Citations
Weidemann, A., Richter, S. , Stein, M., Sahle, S., Gauges, R., Gabdoulline, R., Surovtsova, I., Semmelrock, N., Besson, B., Rojas, I., Wade, R. and Kummer, U. (2008). SYCAMORE - a systems biology computational analysis and modeling research environment.Bioinformatics 24: 1463-1464. Link | ISI Citations | Google Scholar Citations
Flötmann, M., Schaber, J., Hoops, S., Klipp, E. and Mendes, P. (2008). ModelMage: A Tool for Automatic Model Generation, Selection and Management. Genome Informatics 20: 52-63. Link