@article{SM_1968_4_2_a3,
     author = {K. A. Mikhailova},
     title = {The occurrence problem for free products of groups},
     journal = {Sbornik. Mathematics},
     pages = {181--190},
     publisher = {mathdoc},
     volume = {4},
     number = {2},
     year = {1968},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1968_4_2_a3/}
}