@article{KUTGS_1990_20_a8,
     author = {N. N. Perelomova and A. P. Shirokov},
     title = {Second-order tangent bundles of the projective line, and {Lobachevskii} geometry},
     journal = {Trudy Geometricheskogo Seminara},
     pages = {73--85},
     publisher = {mathdoc},
     volume = {20},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/KUTGS_1990_20_a8/}
}