@article{ZNSL_1974_45_a0,
     author = {Yu. D. Burago and V. A. Zalgaller},
     title = {Sufficient conditions for convexity},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {3--52},
     publisher = {mathdoc},
     volume = {45},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1974_45_a0/}
}