ArzhantsevI. V., and PetravchukA. P. “Closed Polynomials and Saturated Subalgebras of Polynomial Algebras”. Ukrains’kyi Matematychnyi Zhurnal 59, no. 12 (December 25, 2007): 1587–1593. Accessed October 6, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3414.