@article{DAN_1983_273_6_a7,
     author = {V. P. Soltan and V. D. Chepoi},
     title = {Some classes of d-convex functions in a graph},
     journal = {Doklady Akademii Nauk},
     pages = {1314--1317},
     publisher = {mathdoc},
     volume = {273},
     number = {6},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1983_273_6_a7/}
}