@article{SM_1996_187_10_a7,
     author = {Yu. S. Semenov},
     title = {Proof of a~generalization of the~conjecture of {Hanna} {Neumann} for virtually free groups},
     journal = {Sbornik. Mathematics},
     pages = {1561--1575},
     publisher = {mathdoc},
     volume = {187},
     number = {10},
     year = {1996},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1996_187_10_a7/}
}