A. Tarmuji, T. Setiadi, S. Handayaningsih, and J. Lestari, “Development of customer relationship management (CRM) model based on the maturity level of cobit 4.1 (Case study: Cooperative section at the department of Industry, trade, cooperative, and small-medium enterprises, Yogyakarta province)”, Asia Pac J Sci Technol, vol. 22, no. 2, pp. APST–22, Apr. 2017.