GEHRING, F.; POMMERENKE, C. Circular distortion of curves and quasicircles. Annales Fennici Mathematici, [S. l.], v. 14, n. 2, p. 381–390, 1989. DOI: 10.5186/aasfm.1989.1406. Disponível em: https://afm.journal.fi/article/view/134672. Acesso em: 9 may. 2024.