@article{MZM_1969_6_5_a1,
     author = {V. V. Borisov},
     title = {Simple examples of groups with unsolvable word problem},
     journal = {Matemati\v{c}eskie zametki},
     pages = {521--532},
     publisher = {mathdoc},
     volume = {6},
     number = {5},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1969_6_5_a1/}
}