@article{JRAM_1966__224_150768,
     author = {N.D. Lane and K.D. Singh},
     title = {Characteristic and order of conically differentiable points.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {164--184},
     publisher = {mathdoc},
     volume = {224},
     year = {1966},
     zbl = {0149.19302},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1966__224_150768/}
}