Bruno W. Häuptli (2004). "Victor IV. (Victor V., Ottaviano de' Monticelli), Gegenpapst 1159-1164". In Bautz, Traugott (ed.). Biographisch-Bibliographisches Kirchenlexikon (BBKL) (in German). Vol. 23. Nordhausen: Bautz. cols. 1533–1536. ISBN3-88309-155-3.; he did not subscribe any papal bulls between 19 February and 14 May 1144 (Jaffé, p.1 and 7)
