We would like to thank:

• Arantza Illarramendi and Serena Sorrentino, for their valuable comments and support.
• The anonymous reviewers of our papers, for their useful suggestions, that helped us to improve our work.
• Víctor Martínez-Burgos, for his work on the graphical user interface.
• Graphics designer José Ilarri, for developing the logo of Doctopush.
• Last but not least, this work was partially supported by the MUR FIRB Network Peer for Business project, the IST FP6 STREP project 2006 STASIS, and the CICYT project TIN2007-68091-C02-02.