SANTOS, Eleonora et al. Productivity Measurement: The Case of Nature Tourism Firms in Portugal. Journal of Tourism, Sustainability and Well-being, [S. l.], v. 8, n. 4, p. 331–346, 2020. Disponível em: https://journals.cinturs.pt/jtsw/article/view/252. Acesso em: 27 oct. 2025.