We consider resonant problems of the type (i) x′′ + p(t)x′ + q(t)x = f (t, x, x′), (ii) x′(0) = 0, x(T) = 0, where p, q, f are continuous functions and the homogeneous problem (iii) x′′ + p(t)x′ + q(t)x = 0 with boundary-value ...