@article{10_4153_CMB_1971_073_3,
     author = {Willett, D.},
     title = {Generalized de la {Vall\'ee} {Poussin} {Disconjugacy} {Tests} for {Linear} {Differential} {Equations(1)}},
     journal = {Canadian mathematical bulletin},
     pages = {419--428},
     year = {1971},
     volume = {14},
     number = {3},
     doi = {10.4153/CMB-1971-073-3},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1971-073-3/}
}