FIDYTEK, Irena. On a functional equation connected with Ptolemaic inequality. Annales Mathematicae Silesianae, [S. l.], v. 15, p. 27–44, 2001. Disponível em: https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/14114. Acesso em: 6 may. 2025.