Marc Daniel. A note on degenerate normal vectors. Computer Aided Geometric Design, 12(8):857-860, 1995. [doi]
@article{Daniel95,
title = {A note on degenerate normal vectors},
author = {Marc Daniel},
year = {1995},
doi = {10.1016/0167-8396(95)00040-9},
url = {http://dx.doi.org/10.1016/0167-8396(95)00040-9},
researchr = {https://researchr.org/publication/Daniel95},
cites = {0},
citedby = {0},
journal = {Computer Aided Geometric Design},
volume = {12},
number = {8},
pages = {857-860},
}