“…This paper continues the series of papers of the authors beginning with the papers of Korpusov et al Moreover, this work is connected with the papers Korpusov et al and Korpusov and Panin of the same series where other initial‐boundary value problems for the same equation have been studied. In the present work, we consider the Equation with the following boundary and initial conditions: We prove a theorem on the nonextendable solution.…”