@article{ZNSL_1977_72_a1,
     author = {A. M. Vershik},
     title = {Many-valued measure-preserving mappings (polymorphisms) and {Markovian} operators},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {26--61},
     year = {1977},
     volume = {72},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1977_72_a1/}
}