HAKIM, S. N.; KALIJAGA, A.; INDRAWATI, S. Service Performance Improvement During Pandemic COVID 19 Using Integrated SERVQUAL and Six Sigma: Telecommunication and Information Industry Case Application. Journal of Industrial Engineering and Halal Industries, [S. l.], v. 1, n. 2, p. 94–101, 2020. Disponível em: https://ejournal.uin-suka.ac.id/saintek/JIEHIS/article/view/2198. Acesso em: 5 dec. 2021.