Estimates for moduli of continuity of functions given by their Fourier transform. - Walter Trebels (Constructive Theory of Functions of Several Variables, 1976)

q-Moduli of Continuity in Hp(D), p>0, and an Inequality of Hardy and Littlewood. - Yuri V. Kryakin; Walter Trebels (J. Approx. Theory, 2002)

On Ulyanov inequalities in Banach spaces and semigroups of linear operators. - Walter Trebels; U. Westphal (J. Approx. Theory, 2009)