@article{DAN_1968_181_5_a2,
     author = {M. A. Gol'dman and S. N. Krachkovskii},
     title = {Products, powers and contractions of homomorphisms},
     journal = {Doklady Akademii Nauk},
     pages = {1038--1041},
     publisher = {mathdoc},
     volume = {181},
     number = {5},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1968_181_5_a2/}
}