Michael R. Fellows Michael T. Hallett Chantal Korostensky Ulrike Stege Analogs and Duals of teh MAST Problem for Sequences and Trees. 103-114 http://link.springer.de/link/service/series/0558/bibs/1461/14610103.htm 1998 conf/esa/1998 ESA db/conf/esa/esa98.html#FellowsHKS98