KUMAR, S. Concentric Arrays of Ring Shaped Apertures as Neutral Density Filters. Defence Science Journal, [S. l.], v. 15, n. 3, p. 165–168, 2014. DOI: 10.14429/dsj.15.7278. Disponível em: https://publications.drdo.gov.in/ojs/index.php/dsj/article/view/7278. Acesso em: 6 jul. 2025.