BIOLCHEVA, Petya; VASIL BOZEV. The Progress of Industry 4.0 in the Conditions of a Pandemic - Bulgarian Case in Natural Gas Sector. Journal of Social Transformation and Regional Development, [S. l.], v. 4, n. 1, p. 1–8, 2022. Disponível em: https://publisher.uthm.edu.my/ojs/index.php/jstard/article/view/11349. Acesso em: 9 apr. 2026.