T. Andini and R. Sayekti, “The Quality of Service at the International Corner in the Library of Universitas Muhammadiyah Sumatera Utara (UMSU) Based on the LibQUAL Model”, JES, vol. 9, no. 4, pp. 2440–2453, Jul. 2025, doi: 10.31258/jes.9.4.p.2440-2453.