MZ Djibibe, K Tcharie, NI Yurchuk - Electronic Journal of Differential …, 2008 - eudml.org
<noindent Electronic Journal of Differential Equations , Vol . 2008 ( 2008 ) , No . 1 7 , pp . 1 --
1 0 ISSN : 1 72 - 6691 . Page 1 <noindent Electronic Journal of Differential Equations , Vol …