Retnawati, B. B., & Nuryakin, N. (2016). Developing Salesperson Performance: The Role of Customer Encountering Competence Portfolio, Relational Capital and Service Excellent Customer Heterogeneity. International Review of Management and Marketing, 6(4), 891–897. Retrieved from https://econjournals.com./index.php/irmm/article/view/3093