LUTHRA, P. N. The technical growth and development of signals. Defence Science Journal, [S. l.], v. 2, n. 2-3, p. 118–125, 1952. DOI: 10.14429/dsj.2.3378. Disponível em: https://publications.drdo.gov.in/ojs/index.php/dsj/article/view/3378. Acesso em: 17 jun. 2025.