Preface: Special Issue Dedicated to Professor Roger Penrose’s 90th Birthday. Communications in Mathematical Research, [S. l.], v. 37, n. 4, p. i-ii, 2022. DOI: 10.4208/cmr.2021.v37n4.preface. Disponível em: https://www.global-sci.com/index.php/cmr/article/view/9056. Acesso em: 5 dec. 2025.