@article{ARM_1976__12_4_a4,
     author = {Ha{\l}kowska, Katarzyna},
     title = {On some operator defined on equational classes of algebras},
     journal = {Archivum mathematicum},
     pages = {209--212},
     publisher = {mathdoc},
     volume = {12},
     number = {4},
     year = {1976},
     mrnumber = {0432510},
     zbl = {0352.08003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ARM_1976__12_4_a4/}
}