DATTA, S. K. Backward-Wave Oscillation Criterion in a Step-Tapered Helix Travelling-Wave Tube. Defence Science Journal, [S. l.], v. 59, n. 1, p. 49–54, 2009. DOI: 10.14429/dsj.59.1484. Disponível em: https://publications.drdo.gov.in/ojs/index.php/dsj/article/view/1484. Acesso em: 13 aug. 2025.