Anggia, Feliks, et al. “Moderation of Personal Relations on Sustainable Competitive Advantages, Customer Relationship Management, and Marketing Performance: Study on Small Scale Business of Leather Products Marketers in East Java”. International Review of Management and Marketing, vol. 7, no. 4, Oct. 2017, pp. 74-82, https://econjournals.org.tr/index.php/irmm/article/view/5135.