ZHEKOVA, Z.; JORDANOV, I. In memoriam проф. Василики Пена (1951-2018): In memoriam Prof. Vasiliki (Vasso) Penna (1951-2018). Numismatics, Sigillography and Epigraphy | Нумизматика, сфрагистика и епиграфика, [S. l.], v. 14, p. 271–273, 2018. Disponível em: https://www.publications.naim.bg/index.php/NSE/article/view/136. Acesso em: 6 nov. 2026.