@article{GDZPPN002485192,
title = {View-Obstruction Problem for 3-dimensional Spheres.},
journal = {Monatshefte f\"ur Mathematik},
volume = {102},
year = {1986},
pages = {279-290},
zbl = {0588.10034},
url = {http://dml.mathdoc.fr/item/GDZPPN002485192}
}
Dumir, V.C.; Hans-Gill, R.J. View-Obstruction Problem for 3-dimensional Spheres.. Monatshefte für Mathematik, Tome 102 (1986) pp. 279-290. http://gdmltest.u-ga.fr/item/GDZPPN002485192/