References
- Guo , D. and Lakshmikantham , V. 1988 . J.Math. Anal Appl., , 129 : 211 – 222 .
- Guo , D. and Lakshmikantham , V. 1988 . “ Nonlinear Problems in Abstract Cones ” . In Acad. Press, Boston Vol. 2 , 1 – 11 . New York, : Boston, .
- Guo , D. 1989 . J.Appl.Math. Simul., , 2 : 1 – 11 .
- Lakshmikantham , V. 1981 . “ Nonlinear Differential Equations in Abstract Spaces, ” . Edited by: Leela , S. Oxford, : Pergamon Press .