@article{ZNSL_1978_75_a15,
     author = {E. B. Plotkin},
     title = {A property of root systems},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {151--153},
     year = {1978},
     volume = {75},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1978_75_a15/}
}