Sustainability in the hospitality industry in the shadow of the COVID-19 pandemic: a case study of the hospitality industry in PolandPaweł Dahlke, Katarzyna Orfin-Tomaszewska and Piotr SosnowskiE3S Web Conf., 307 (2021) 08002DOI: https://doi.org/10.1051/e3sconf/202130708002