Baharudin, B., R. Hakim, R. Hidayat, M. A. Fikri, and A. D. Wilujeng. “Preliminary Design of Wellhead Spacer Spool Based On the API Acceptance Criteria”. Journal of Energy, Mechanical, Material, and Manufacturing Engineering, vol. 6, no. 1, Apr. 2021, pp. 15-24, doi:10.22219/jemmme.v6i1.11879.