Hakim, S. N., Kalijaga, A., & Indrawati, S. (2020). 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, 1(2), 94–101. https://doi.org/10.14421/jiehis.2198