Bavula, V. V. “Extreme Modules over the Weyl Algebra $A_n$”. Ukrains’kyi Matematychnyi Zhurnal 45, no. 9 (September 25, 1993): 1187–1197. Accessed April 11, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5920.