Mashabai, I., and A. M. . Irahayu Asran. “Analysis of Downtime Problems on Elevator Machine at PT. Santosa Utama Lestari Using Tree Diagrams”. SAINTEKBU, vol. 15, no. 01, June 2023, pp. 9-14, doi:10.32764/saintekbu.v15i01.3258.