A Note on Minimal Covers.

http://doi.acm.org/10.1145/61733.61734 db/journals/sigmod/Atkins88.html John Atkins A Note on Minimal Covers. 16-21 sigmodR/17-4/P016.pdf 1988 17 SIGMOD Record 4 db/journals/sigmod/sigmod17.html#Atkins88