Reviews and References
Official Agencies of the Turismo de Portugal
Portugal Trails listed on the Tourism of Portugal
License nr. 2791 (Turismo de Portugal, I.P.) RNAVT (Registo Nacional das Agências de Viagens e Turismo)
International Travel News
“Our trip was arranged by Spain Trails (Cascais, Portugal; spaintrails.com), which offers custom travel packages” By Edward Sylvester (2018), International Travel News, November.