N. J. Doneva, Z. Despodov, D. Mirakovski, M. Hadzi-Nikolova, and S. Mijalkovski, “COST ANALYSIS IN CONSTRUCTION OF UNDERGROUND MINING STRUCTURES AND OPPORTUNITIES FOR THEIR REDUCTION”, Rud.-geol.-naft. zb., vol. 30, no. 2, pp. 1–12, Sep. 2015.