@article{ZNSL_1969_15_a7,
     author = {T. F. Pankratova},
     title = {About eigen oscillations in the ring resonator},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {122--141},
     year = {1969},
     volume = {15},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1969_15_a7/}
}