Radim Belohlávek Jan Outrata Vilém Vychodil Direct Factorization by Similarity of Fuzzy Concept Lattices by Factorization of Input Data. 68-79 2006 CLA http://dx.doi.org/10.1007/978-3-540-78921-5_4 conf/cla/2006 db/conf/cla/cla2006.html#BelohlavekOV06