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ZernovA. E.; KuzinaY. V. Qualitative Investigation of the Singular Cauchy Problem <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>′) = 0, <em class="a-Plus-plus">x</Em&gt;(0) = 0. Ukr. Mat. Zhurn. 2003, 55, 1720-1723.