@article{MOMA_1986__101_178279,
     author = {V.C. Dumir and R.J. Hans-Gill},
     title = {View-Obstruction {Problem} for 3-dimensional {Spheres.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {279--290},
     publisher = {mathdoc},
     volume = {101},
     year = {1986},
     zbl = {0588.10034},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1986__101_178279/}
}