1. "Tourism and the City: The Impact of Tourism on Lisbon" by António Freitas and Maria do Carmo Gomes (2017): https://www.sciencedirect.com/science/article/pii/S2212041617302083
2. "Cultural Tourism in Lisbon: A Study of Its Economic and Social Impacts" by João Costa, Pedro Costa and João Freitas (2013): https://www.researchgate.net/publication/257568681_Cultural_Tourism_in_Lisbon_A_Study_of_Its_Economic_and_Social_Impacts
3. "Sustainability and the Challenges of Tourism in Lisbon: A Critical Study" by Inês Cunha and António Freitas (2018): https://link.springer.com/article/10.1007/s40888-018-0107-6
4. "The Impact of Tourism on the Economic Growth in Lisbon, Portugal" by Catarina Sousa (2018): https://scholarworks.rit.edu/cgi/viewcontent.cgi?article=3109&context=theses
5. "Lisbon’s Cultural Tourism: The Impact of Local Cultural Identities on Tourist Experience" by Débora Pires and Luís Menezes Leitão (2018): https://www.researchgate.net/publication/328173354_Lisbon's_Cultural_Tourism_The_Impact_of_Local_Cultural_Identities_on_Tourist_Experience