Prokip, V. M. “On Multiplicativity of Canonical Diagonal Forms of Matrices over the Domain of Principal Ideals. II”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 53, no. 2, Feb. 2001, pp. 274-7, https://umj.imath.kiev.ua/index.php/umj/article/view/4246.