Br Sinulingga, N. A., R. Kartika Lubis, H. Raq, and A. D. Stephanie. “Antecedents Relationship Commitment to Postpaid Service Products During the Covid 19 Pandemic”. Enrichment : Journal of Management, Vol. 12, no. 1, Oct. 2021, pp. 527-33, doi:10.35335/enrichment.v12i1.260.