@article{TIMM_2018_24_2_a4,
     author = {V. I. Berdyshev},
     title = {Characterization of optimal trajectories in $\mathbb {R}^3$},
     journal = {Trudy Instituta matematiki i mehaniki},
     pages = {40--45},
     year = {2018},
     volume = {24},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TIMM_2018_24_2_a4/}
}