Martins, António. Portugal (1185–1248). Portugal. Flags of the World. [2007-02-22]. (原始内容存档于2006-07-19). A Bandeira de Portugal. Portugal. Criar Mundos.
Conflicts and the Transformation of Europe London (2000) ISBN 0-415-21454-8 HistoryofPortugal by the Office of the Secretary of State for Information and Tourism