Rocío González-Díaz Pedro Real Towards Digital Cohomology. 92-101 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2886&spage=92 2003 conf/dgci/2003 DGCI db/conf/dgci/dgci2003.html#Gonzalez-DiazR03