the composition of two linear operators acting on an arbitrary Banach space. … If f has
continuous derivatives of higher degree, the above Voronovskaya formula can be extended;
see, eg, [4] and the references therein. The investigation of Voronovskaya-type formulas for
the composition of two linear operators Pn and Qn, acting on an arbitrary Banach space X,
was initiated in [4]. …