Luca Aceto Jens A. Hansen Anna Ingólfsdóttir Jacob Johnsen John Knudsen The Complexity of Checking Consistency of Pedigree Information and Related Problems. 42-59 2004 19 J. Comput. Sci. Technol. 1 http://jcst.ict.ac.cn/cone/cone41.html#paper5 db/journals/jcst/jcst19.html#AcetoHIJK04