RadzievskayaE.I. and RadzievskiiG.V. 2003. 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. Ukrains’kyi Matematychnyi Zhurnal. 55, 11 (Nov. 2003), 1530-1540.