@article{AL_1984_23_2_a5,
     author = {A. A. Stepanova},
     title = {Groupoids of rank $2$ generating categorical {Horn} classes},
     journal = {Algebra i logika},
     pages = {193--207},
     publisher = {mathdoc},
     volume = {23},
     number = {2},
     year = {1984},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1984_23_2_a5/}
}