José Vicente Álvarez-Bravo Juan Carlos Peris M. Teresa Escrig J. J. Álvarez-Sánchez F. J. González-Cabrera A Qualitative Representation Model about Trajectories in 2-D. 124-136 2006 CCIA conf/ccia/2006 db/conf/ccia/ccia2006.html#Alvarez-BravoPEAG06 http://www.booksonline.iospress.nl/Content/View.aspx?piid=2092