Vasylyshyn, T.V. “Description of Spectra and Derivations of Wiener Type Algebras of Functions Generated by $(p,q)$-Polynomials on Banach Spaces”. Carpathian Mathematical Publications, vol. 4, no. 2, Dec. 2012, pp. 212-28, https://ktipe.pnu.edu.ua/index.php/cmp/article/view/2157.