"Steven Petkov é Viriato até 2024" [Steven Petkov is Viriato until 2024] (in European Portuguese). Académico de Viseu. 28 August 2023. Retrieved 3 October 2023.
"Petkov emprestado ao Levski Sofia" [Petkov loaned to Levski Sofia]. CD Feirense (in European Portuguese). 14 September 2020. Retrieved 13 August 2023.