@article{10_4153_CMB_1974_071_5,
     author = {Shum, D. T.},
     title = {A {General} and {Sharpened} form of {Opial's} {Inequality}},
     journal = {Canadian mathematical bulletin},
     pages = {385--389},
     year = {1974},
     volume = {17},
     number = {3},
     doi = {10.4153/CMB-1974-071-5},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1974-071-5/}
}