@article{AL_1977_16_6_a1,
     author = {Yu. L. Ershov},
     title = {Numeration of the class $\mathbb{C}^*_{20}$},
     journal = {Algebra i logika},
     pages = {637--642},
     publisher = {mathdoc},
     volume = {16},
     number = {6},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1977_16_6_a1/}
}