@article{MAT_1960_4_1_a1,
     author = {A. Shapiro and J. H. Whitehead},
     title = {A proof and extension of {Dehn's} lemma},
     journal = {Matematika},
     pages = {9--14},
     publisher = {mathdoc},
     volume = {4},
     number = {1},
     year = {1960},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MAT_1960_4_1_a1/}
}