@article{ZNSL_1986_154_a10,
     author = {A. Yu. Nenashev},
     title = {On {Hecke} operators for a~principal congruence-subgroups},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {130--135},
     publisher = {mathdoc},
     volume = {154},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1986_154_a10/}
}