Kahlig, Peter, and Janusz Matkowski. “On Some Extensions of the Gołąb-Schinzel Functional Equation”. Annales Mathematicae Silesianae 8 (September 30, 1994): 13-31. Accessed May 18, 2024. https://www.journals.us.edu.pl/index.php/AMSIL/article/view/14214.