Ariga, R. A., R. Amelia, S. B. Astuti, F. A. A. Fajar, S. Ariga, H. P. S. Ariga, and N. K. Pane. “Implementation of Lean Six Sigma in Improving Competitive Advantage through Patient Satisfaction and Nurse Resources to Face the Covid-19 Pandemic at USU Medan Hospital”. Open Access Macedonian Journal of Medical Sciences, vol. 10, no. G, Feb. 2022, pp. 218-22, doi:10.3889/oamjms.2022.7888.