Akulov , V.F. and Shishkov , A.E. (1992) “Uniqueness of solutions of mixed problems and the Cauchy problem for parabolic equation of high order with nonrestricted coef¬ficients”, Ukrains’kyi Matematychnyi Zhurnal, 44(2), pp. 149–155. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/7826 (Accessed: 16 April 2025).