ALT, Heinrich. Platonisme, konseptualisme en nomimalisme in die versamelingsteorie. Tydskrif vir Christelike Wetenskap | Journal for Christian Scholarship, [S. l.], v. 57, n. 3&4, p. 31–52, 2021. Disponível em: https://pubs.ufs.ac.za/index.php/tcw/article/view/557. Acesso em: 5 oct. 2025.