Łobos, K., and M. Szewczyk. “Impact of Intangible Assets on the Economic Effectiveness As Illustrated by National Enterprises in the Manufacturing Mushroom Compost”. Journal of Agribusiness and Rural Development, Vol. 27, no. 1, Dec. 2013, pp. 143-52, http://www1.up.poznan.pl/jard/index.php/jard/article/view/600.