L. Oxamudra, S. Noya, Y. Ekawati, N. K. Putrianto, T. Oktiarso, and P. Purnomo, “Quality Improvement Analysis of X Brand Tube Packaging Using Six Sigma and Failure Mode and Effects Analysis (FMEA)”, SAKTI, vol. 5, no. 02, pp. 111–124, Dec. 2025.