@article{IVM_1975_7_a4,
     author = {G. Z. Zlatanov and A. P. Norden},
     title = {Orthogonal trajectories of a~geodesic field},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {42--46},
     year = {1975},
     number = {7},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1975_7_a4/}
}