1. Student in the Doctoral Program of Management Science, Universitas Sumatera Utara [University of North Sumatra]
2. Dr., Associate Professor, Department of Management, Faculty of Economics and Business, Universitas Sumatera Utara
3. Prof., Lecturer, Faculty of Economics and Business, Universitas Sumatera Utara [University of North Sumatra]
4. Dr., Associate Professor, Faculty of Economics and Business, Universitas Sumatera Utara [University of North Sumatra]