Mikołajczak, Paweł. “The Impact of the Diversification of Revenues on NGOs’ Commercialization: Evidence from Poland”. Equilibrium. Quarterly Journal of Economics and Economic Policy 13, no. 4 (December 31, 2018): 761-779. Accessed July 22, 2019. http://economic-research.pl/Journals/index.php/eq/article/view/1130.