@article{MZM_1977_22_4_a13,
     author = {G. P. Egorychev and Yu. D. Ushakov},
     title = {The ranks of the $p$-central series of free groups of certain manifolds},
     journal = {Matemati\v{c}eskie zametki},
     pages = {575--582},
     publisher = {mathdoc},
     volume = {22},
     number = {4},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1977_22_4_a13/}
}