Simanjuntak, Loranty Folia, et al. “Analysis of Coffee MSME Production Cost Efficiency Using the Leontief Matrix Model Based on Monthly Production Data at Sumatra Roastery in Medan City”. Outline Journal of Economic Studies, vol. 5, no. 2, Apr. 2025, pp. 124-32, https://doi.org/10.61730/vegjaa70.