1. The Linnaeus Centre for Bioinformatics, Uppsala University BMC, Box 598, Husargatan 3, SE-751 24 Uppsala, Sweden.
2. Interdisciplinary Centre for Mathematical and Computational Modelling, Warsaw University, ul.Żwirki i Wigury 93, 02-089 Warszawa, Poland.
3. Institute of Computer Science, Polish Academy of Sciences, ul. J.K. Ordona 21, 01-237 Warszawa, Poland.