Martin Gavalec Solvability and unique solvability of max-min fuzzy equations. 385-393 2001 124 Fuzzy Sets and Systems 3 http://www.sciencedirect.com/science/article/B6V05-445G529-D/2/6e9a912ac73e94da232c731170e77457 db/journals/fss/fss124.html#Gavalec01