Wijaya, A., J. Soedarsono, and A. Laksana. “The Study of Mixing Purple Sweet Potato and Turmeric Extract As Green Corrosion Inhibitor for API-5L in NaCl 3,5% Environment”. Jurnal Pendidikan Teknologi Kejuruan, Vol. 4, no. 4, Dec. 2021, pp. 140-5, doi:10.24036/jptk.v4i4.21823.