@article{MMO_1970_21_a5,
     author = {B. M. Rudyk},
     title = {Extensions of modules},
     journal = {Trudy Moskovskogo matemati\v{c}eskogo ob\^{s}estva},
     pages = {209--244},
     year = {1970},
     volume = {21},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MMO_1970_21_a5/}
}