@article{ZNSL_1981_117_a8,
     author = {A. P. Katchalov},
     title = {The weak inhomogeneous optical fiber},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {134--146},
     publisher = {mathdoc},
     volume = {117},
     year = {1981},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1981_117_a8/}
}