@article{DAN_1957_116_1_a5,
     author = {A. I. Mal'tsev},
     title = {On derivative operations and predicates},
     journal = {Doklady Akademii Nauk},
     pages = {24--27},
     publisher = {mathdoc},
     volume = {116},
     number = {1},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_116_1_a5/}
}