@article{SF_1992__45_3_135165,
     author = {Ju.G. Koselev},
     title = {On a multiplication  of semigroup varieties.},
     journal = {Semigroup forum},
     pages = {1--8},
     publisher = {mathdoc},
     volume = {45},
     number = {3},
     year = {1992},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SF_1992__45_3_135165/}
}