[1]
RadzievskayaE. I. and RadzievskiiG. V., “Estimation of a <em class="a-plus-plus">K</em>-Functional of Higher Order in Terms of a <em class="a-plus-plus">K</em&gt;-Functional of Lower Order”, Ukr. Mat. Zhurn., vol. 55, no. 11, pp. 1530-1540, Nov. 2003.