"Kelvin" (in Portuguese). Mais Futebol. Retrieved 10 February 2022.
Alvarenga, Vítor Hugo (1 December 2012). "F.C. Porto: Iturbe e Kelvin jogam pela equipa B" [F.C. Porto: Iturbe and Kelvin play for the B team] (in Portuguese). Mais Futebol. Retrieved 10 February 2022.