Necessary and sufficient conditions for boundedness of the Hardy-type operator from a weighted Lebesgue space to a Morrey-type space V. I. Burenkov, R. Oinarov Mathematical Inequalities & Applications (1331-4343) 2013 vol.16 no.1 pp.1-19 http://mia.ele-math.com/volume/16/issue/1 On fractional smoothness of functions related to p-variation Martin Lind Mathematical Inequalities & Applications (133..