@article{ZNSL_1994_218_a2,
     author = {M. I. Belishev},
     title = {On a~justification of the {Huygens's} {Rule}},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {17--24},
     publisher = {mathdoc},
     volume = {218},
     year = {1994},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1994_218_a2/}
}