@article{DAN_1975_221_5_a3,
     author = {V. N. Kas'yanov},
     title = {Distinguishing hammocks in a directed graph},
     journal = {Doklady Akademii Nauk},
     pages = {1020--1022},
     publisher = {mathdoc},
     volume = {221},
     number = {5},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1975_221_5_a3/}
}