1. Technical University of Gabrovo,Department of Machine and Precision Engineering,Gabrovo,Bulgaria
2. Technical University of Sofia,Department of Precision Engineering and Measurement Instruments,Sofia,Bulgaria
3. Ukrainian Engineering Pedagogics Academy,Department of Information Computer Technologies and Mathematics,Kharkiv,Ukraine
4. Technical University of Sofia,Department of Automation of Discrete Production Engineering,Sofia,Bulgaria
5. Technical University of Gabrovo,Department of Mechanical Engineering Technology and Machine Tools,Gabrovo,Bulgaria
6. Technical University of Gabrovo,Department of Mathematics Informatics and Natural Sciences,Gabrovo,Bulgaria