Peter Dybjer Qiao Haiyan Makoto Takeyama Random Generators for Dependent Types. 341-355 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3407&spage=341 2004 conf/ictac/2004 ICTAC db/conf/ictac/ictac2004.html#DybjerHT04