@article{10_4153_CJM_1993_027_9,
     author = {Dumir, V. C. and Hans-Gill, R. J. and Wilker, J. B.},
     title = {Contributions to a {General} {Theory} of {View-Obstruction} {Problems}},
     journal = {Canadian journal of mathematics},
     pages = {517--536},
     year = {1993},
     volume = {45},
     number = {3},
     doi = {10.4153/CJM-1993-027-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1993-027-9/}
}