Sufficient conditions for the existence of nonnegative solutions of a nonlocal boundary value problem. - George L. Karakostas; P. Ch. Tsamatos (Appl. Math. Lett., 2002)

Global solutions of a singular initial value problem to second order nonlinear delay differential equations. - Ravi P. Agarwal; Christos G. Philos; P. Ch. Tsamatos (Math. Comput. Model., 2006)