@article{10_4153_CJM_1975_071_9,
     author = {Jonker, Leo B.},
     title = {Immersions with {Semi-Definite} {Second} {Fundamental} {Forms}},
     journal = {Canadian journal of mathematics},
     pages = {610--617},
     year = {1975},
     volume = {27},
     number = {3},
     doi = {10.4153/CJM-1975-071-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1975-071-9/}
}