Petrova D, Vlahova B, Lengerov A, Zlateva-Petkova T. STUDY OF THE STATE OF INNOVATION DEVELOPMENT AND OBSOLESCENCE IN THE REPUBLIC OF BULGARIA OF COMPANIES FROM THE MECHANICAL ENGINEERING SECTOR. ETR [Internet]. 2023 Jun. 13 [cited 2024 Dec. 15];1:187-94. Available from: https://journals.rta.lv/index.php/ETR/article/view/7239