Linear cross-sections and Fredholm operators in a class groupoid $C^*$-algebras. Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 108, p. 17–21, 2021. DOI: 10.60063/gsu.fmi.108.17-21. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/550. Acesso em: 14 dec. 2025.