@article{GDZPPN002026945,
title = {View-Obstruction Problems},
journal = {Aequationes mathematicae},
volume = {9},
year = {1973},
pages = {165-170},
zbl = {0265.52003},
url = {http://dml.mathdoc.fr/item/GDZPPN002026945}
}
CUSICK, T.W. View-Obstruction Problems. Aequationes mathematicae, Tome 9 (1973) pp. 165-170. http://gdmltest.u-ga.fr/item/GDZPPN002026945/