@article{10_4153_CMB_1993_064_4,
     author = {Ruan, Shigui},
     title = {Oscillations of {Second} {Order} {Neutral} {Differential} {Equations}},
     journal = {Canadian mathematical bulletin},
     pages = {485--496},
     year = {1993},
     volume = {36},
     number = {4},
     doi = {10.4153/CMB-1993-064-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1993-064-4/}
}