Rinaldo, H., and W. Sulistiyowati. “Donut Production Sigma Level and Strategic Positioning: Tingkat Sigma Produksi Donat Dan Posisi Strategis”. Indonesian Journal of Innovation Studies, vol. 26, no. 2, Feb. 2026, p. 10.21070/ijins.v26i2.2032, doi:10.21070/ijins.v26i2.2032.