Jecheva, Ginka, Tihomir Dovramadjiev, Momchil Tachev, and Kremena Markova. ANNUAL JOURNAL OF TECHNICAL UNIVERSITY OF VARNA, BULGARIA 2, no. 2 (December 20, 2018): 46-53. Accessed August 20, 2025. http://194.141.24.9/index.php/ajtuv/article/view/91.