Zvozdetskyi, T.I. “On the $n$-Similarity of the Operators Which Are Left Inverse to the $n^{th}$ Degree of the Integration Operator in the Spaces of Analytic Functions”. Carpathian Mathematical Publications, vol. 4, no. 2, Dec. 2012, pp. 261-7, https://journals.pnu.edu.ua/index.php/cmp/article/view/2270.