@article{ZNSL_2018_471_a12,
     author = {M. M. Popov},
     title = {On {Morse} index for geodesic lines on smooth surfaces imbedded in~$\mathbb R^3$},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {211--224},
     publisher = {mathdoc},
     volume = {471},
     year = {2018},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2018_471_a12/}
}