@article{10_4153_CMB_1971_096_8,
     author = {Willett, D.},
     title = {Oscillation on {Finite} or {Infinite} {Intervals} of {Second} {Order} {Linear} {Differential} {Equations(1)}},
     journal = {Canadian mathematical bulletin},
     pages = {539--550},
     year = {1971},
     volume = {14},
     number = {4},
     doi = {10.4153/CMB-1971-096-8},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1971-096-8/}
}