Ferran Naya Manuel Contero Nuria Aleixos Joaquim A. Jorge 613-621 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3044&spage=613 2004 conf/iccsa/2004-2 ICCSA (2) db/conf/iccsa/iccsa2004-2.html#NayaCAJ04