ZERNOV, A. E.; KUZINA, Y. V. Asymptotic Behavior of Solutions of the Cauchy Problem <em class="a-plus-plus">x</em>′ = <em class="a-plus-plus">f</em>(<em class="a-plus-plus">t</em>, <em class="a-plus-plus">x</em>, <em class="a-plus-plus">x</em>′), <em class="a-plus-plus">x</em&gt;(0) = 0. Ukrains’kyi Matematychnyi Zhurnal, v. 54, n. 12, p. 1698-1703, 25 Dec. 2002.