Prokip, V. M. “To the Problem of Multiplicativity of Canonical Diagonal Forms of Matrices over the Domain of Principal Ideals”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 47, no. 11, Nov. 1995, pp. 1581–1584, https://umj.imath.kiev.ua/index.php/umj/article/view/5551.