Memoria Anual 2019(PDF). Metro Bilbao (Report) (in Spanish). p. 30. Retrieved 4 April 2023.
metrobilbao.net
"El metro que pudo ser"(PDF). Metroberri (in Spanish). No. 17. Metro Bilbao. June 2000. p. 6. Archived from the original(PDF) on 4 July 2010. Retrieved 2 October 2021.
"El metro que pudo ser"(PDF). Metroberri (in Spanish). No. 17. Metro Bilbao. June 2000. p. 6. Archived from the original(PDF) on 4 July 2010. Retrieved 2 October 2021.