“…Ptashnyk et al [45,46,47]. The problems with the local multipoint conditions were considered in [48,50], with the nonlocal conditions in [22,23,27,47] (in the complex domain in [28]), with the integral conditions in [25,26]. The question of how to estimate the small denominators with complicated nonlinear structure is common for all types of multipoint problems ( [24,27,47]).…”