M. Janiak, “The expansion of international hotel systems (IHS) as a research issue in Polish and foreign academic literature”, in Percepcja turystyki w przestrzeni i w czasie pandemii COVID-19, vol. 12, M. Makowska-Iskierka and J. Wojciechowska, Eds. Poland: Lodz University Press, 2022, pp. 103–123. doi: 10.18778/8220-907-5.06.