SITINJAK, T. J. R.; STEFFEN, E. THE EFFECT OF PRODUCT QUALITY AND SERVICE QUALITY ON CUSTOMER LOYALTY OF WARUNK UPNORMAL. Jurnal Manajemen, [S. l.], v. 10, n. 2, p. 21–33, 2021. DOI: 10.46806/jm.v10i2.740. Disponível em: https://jurnal.kwikkiangie.ac.id/index.php/JM/article/view/740. Acesso em: 9 oct. 2025.