@article{10_4153_CJM_1970_051_9,
     author = {Petty, C. M. and Crotty, J. M.},
     title = {Characterizations of {Spherical} {Neighbourhoods}},
     journal = {Canadian journal of mathematics},
     pages = {431--435},
     year = {1970},
     volume = {22},
     number = {2},
     doi = {10.4153/CJM-1970-051-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1970-051-9/}
}