Department of Mathematics and Computer Sciences, Faculty of Sciences, University of Maroua,
Maroua, Cameroon;Department of Mathematics, Faculty of Sciences, University of Yaounde 1, Yaounde, Cameroon
;
University of Lorraine, Lorraine, France
Copyright © 2014 Didier Alain Njamen-Njomen, Joseph Ngatchou-Wandji et al. This is
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