BREWER, C.; CAMPBELL, A. J. Beyond Graduated Circles: Varied Point Symbols for Representing Quantitative Data on Maps. Cartographic Perspectives, [S. l.], n. 29, p. 6–25, 1998. DOI: 10.14714/CP29.672. Disponível em: https://cartographicperspectives.org/index.php/journal/article/view/cp28-brewer-campbell. Acesso em: 24 apr. 2024.