Penawan, A., and - Setiyana. “STRATEGI PENINGKATAAN LOYALITAS UPK GONDANGREJO KARANGANYAR”. Dinamika Ekonomi: Jurnal Ekonomi Dan Bisnis, Vol. 14, no. 1, Mar. 2021, pp. 48-66, https://stienas-ypb.ac.id/jurnal/index.php/jdeb/article/view/309.