@article{10_4153_CMB_1969_034_4,
     author = {Swanson, C.A.},
     title = {Nonoscillation {Criteria} for {Elliptic} {Equations}},
     journal = {Canadian mathematical bulletin},
     pages = {275--280},
     year = {1969},
     volume = {12},
     number = {3},
     doi = {10.4153/CMB-1969-034-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1969-034-4/}
}