@article{MZM_1974_15_2_a11,
     author = {A. I. Budkin},
     title = {Semivarieties and {Schreier} varieties of unary algebras},
     journal = {Matemati\v{c}eskie zametki},
     pages = {263--270},
     publisher = {mathdoc},
     volume = {15},
     number = {2},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1974_15_2_a11/}
}