Luca Aceto Jens A. Hansen Anna Ingólfsdóttir Jacob Johnsen John Knudsen The Complexity of Checking Consistency of Pedigree Information and Related Problems. 174-187 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2841&spage=174 2003 conf/ictcs/2003 ICTCS db/conf/ictcs/ictcs2003.html#AcetoHIJK03