@article{RM_1977_32_1_a28,
     author = {Yu. I. Lyubich},
     title = {Nilpotency of commutative {Engel} algebras of dimension $n\leqslant 4$ over~$R$},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     year = {1977},
     volume = {32},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1977_32_1_a28/}
}