Flexible querying via if-sets.

Przemyslaw Grzegorzewski Edyta Mrówka Flexible querying via if-sets. 587-597 2007 22 Int. J. Intell. Syst. 6 http://dx.doi.org/10.1002/int.20215 db/journals/ijis/ijis22.html#GrzegorzewskiM07