Atanasov, Atanas, and Angel Lengerov. 2021. “INCREASING THE EFFECIENCY OF LASER MARKING OFALUMINUM ALLOYS BY DOUBLE WRITING OF THE SYMBOLS”. ENVIRONMENT. TECHNOLOGY. RESOURCES. Proceedings of the International Scientific and Practical Conference 3 (June): 20-24. https://doi.org/10.17770/etr2021vol3.6550.