Hadzik, A., A. Szromek, and D. Żylak. “COMPETITIVENESS OF THE TOURISM PRODUCT OF KOŁOBRZEG SPA”. Acta Scientiarum Polonorum. Oeconomia, Vol. 9, no. 4, Dec. 2010, pp. 153-64, https://js.wne.sggw.pl/index.php/aspe/article/view/3944.