LEITZELL, M.; MACEACHREN, A. Systat. Cartographic Perspectives, [S. l.], n. 04, p. 11–12, 1989. DOI: 10.14714/CP04.1140. Disponível em: https://cartographicperspectives.org/index.php/journal/article/view/cp04-leitzell-maceachren. Acesso em: 5 may. 2024.