1. On nonlinear contractions;Boyd,1969
2. A theorem on contraction mappings;Meir;J. Math. Anal. Appl.,1969
3. Comparison principle and nonlinear contractions in abstract spaces;Eisenfeld;J. Math. Anal. Appl.,1975
4. On a boundary value problem for a class of differential equations with a deviating argument;Eisenfeld;J. Math. Anal. Appl.,1975
5. J. Eisenfeld and V. Lakshmikantham, Existence and estimates for solutions of nonlinear equations near a branch point, Technical Report No. 3, University of Texas at Arlington.