BIKELIS, A. On the multivariate characteristic functions. Lithuanian Mathematical Journal, [S. l.], v. 8, n. 1, p. 21–39, 1968. DOI: 10.15388/LMJ.1968.20178. Disponível em: https://www.zurnalai.vu.lt/LMJ/article/view/20178. Acesso em: 8 jun. 2025.