M. Nores, J. Arias, J. Duque, and Y. Blanco-Fernández. HEALTHINF (2), page 167-172. INSTICC - Institute for Systems and Technologies of Information, Control and Communication, (2008)978-989-8111-16-6.
N. Kanhabua, R. Blanco, and M. Matthews. Proceedings of the 34th international ACM SIGIR conference on Research and development in Information Retrieval, page 755--764. New York, NY, USA, ACM, (2011)