@article{AL_1980_19_5_a3,
     author = {E. A. Palyutin},
     title = {Categorical {Horn} classes. {I}},
     journal = {Algebra i logika},
     pages = {582--614},
     publisher = {mathdoc},
     volume = {19},
     number = {5},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1980_19_5_a3/}
}