Sousa, M. J., V. Santo, A. Sacavém, I. P. dos Reis, and M. C. Sampaio. “4.0 Leadership Skills in Hospitality Sector”. Journal of Reviews on Global Economics, vol. 8, Feb. 2019, pp. 105-17, https://www.lifescienceglobal.com/pms/index.php/jrge/article/view/5849.