Ger, Joanna. “On Analytic Solutions of the Equation ϕ(f(x)) = g(x,ϕ(x)) (III)”. Annales Mathematicae Silesianae 1 (September 30, 1985): 93–102. Accessed May 6, 2025. https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/14339.