ALRASHID, E. R. Human Sigma Optimization: Improving Employee Engagement. Jurnal Manajemen dan Bisnis Madani, [S. l.], v. 1, n. 2, p. 159-167, 2019. Disponível em: https://journal.paramadina.ac.id/index.php/madani/article/view/151. Acesso em: 29 apr. 2024.