AKSAKAL, OZKAN, YUSUF KAYA, and MERYEM SENGUL. 2010. “Biosorption of Copper(II) Ion From Aqueous Solutions Using Caucasian Fir (Abies Nordmanniana (Stev.) Spach. Subsp. Nordmanniana) Cones”. Asian Journal of Chemistry 21 (4):3073-80. https://asianpubs.org/index.php/ajchem/article/view/12425.