Dimovska, Snežana, Trajče Stafilov, and Robert Šajn. 2013. “Determination of Activity Concentration of 40K and Gross Beta Activity in Soil from Kavadarci and Its Environs”. Geologica Macedonica 24 (1/2), pp.53-62. https://js.ugd.edu.mk/index.php/GEOLMAC/article/view/261.