Font, Xavier e Harris, Catherine (2004) Rethinking standards form green to sustainable, Annals of Tourism Research 31(4), 986-1007. null
Mehmetoglu, M. (2007) Typologising nature-based tourists by activity: theoretical and practical implications, Tourism Management 28: 651-660 null
Huybers, Twan e Bennett, Jeff (2002) Environmental management and the competitiveness of nature-based tourism destinations, Cheltenhan, Edward Elgar Publishing, 172 p null
Higham, J. e Lück, M. (2002) Urban Ecotourism: A Contradiction in Terms?, Journal of Ecotourism 1 (1): 36-51. null
Katila, M. e Puustjärvi, E. (2004) Markets for forest environmental services: reality and potential, Unasylva 219 (55): 53-58. null
Patacho, Mª Madalena (2010) Comparação de programas de certificação em Ecoturismo, Évora, Universidade de Évora / ISA (dissertação de mestrado). null
Bien, A. (2006) A Simple User’s Guide to Certificationfor sustainable Tourism an Ecotourism, CESD. null