D. LI, H. Queffélec, and L. Rodriguez-Piazza, “Composition operators with surjective symbol and small approximation numbers”, NWEJM, no. 5, pp. 1–20, Feb. 2019, Accessed: Nov. 24, 2024. [Online]. Available: https://nwejm.univ-lille.fr/index.php/nwejm/article/view/36