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@article{CC_2007_36_3_a8, author = {Cegielski, Andrzej}, title = {A generalization of the {Opial's} theorem}, journal = {Control and Cybernetics}, pages = {601--610}, publisher = {mathdoc}, volume = {36}, number = {3}, year = {2007}, zbl = {1190.47067}, language = {en}, url = {http://geodesic.mathdoc.fr/item/CC_2007_36_3_a8/} }
Cegielski, Andrzej. A generalization of the Opial's theorem. Control and Cybernetics, Tome 36 (2007) no. 3, pp. 601-610. http://geodesic.mathdoc.fr/item/CC_2007_36_3_a8/