Gerd Stumme Rafik Taouil Yves Bastide Nicolas Pasquier Lotfi Lakhal Computing iceberg concept lattices with T. 189-222 2002 42 Data Knowl. Eng. 2 db/journals/dke/dke42.html#StummeTBPL02 http://dx.doi.org/10.1016/S0169-023X(02)00057-5