@article{IVM_1970_7_a1,
     author = {L. M. Berkovich},
     title = {Certain classes of difference and differential equations with variable coefficients},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {13--25},
     year = {1970},
     number = {7},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1970_7_a1/}
}