Skorwider-Namiotko, J., A. Skorwider-Namiotko, and M. Dębniewska. “Own Investment Capacity of Communes in Naturally Valuable Areas and Local Conditions of Tourism Development”. Economics and Environment, vol. 66, no. 3, June 2018, p. 13, https://ekonomiaisrodowisko.pl/journal/article/view/148.