Authors
Miroslav Vasilev
Trakia University, Faculty of Technics and Technologies, Yambol, Bulgaria
Galya Shivacheva
Trakia University, Faculty of Technics and Technologies, Yambol, Bulgaria
Vanya Stoykova
Trakia University, Faculty of Technics and Technologies, Yambol, Bulgaria
Zlatin Zlatev
Trakia University, Faculty of Technics and Technologies, Yambol, Bulgaria
