Siswanto, Budi, et al. “Improvement of Preventive Maintenance Process Effectiveness in Insourcing and Outsourcing Scheme With House of Risk (HOR) Method Approach (A Case Study)”. IPTEK The Journal for Technology and Science, vol. 30, no. 2, July 2025, pp. 52-55, https://journal.its.ac.id/index.php/jts/article/view/4340.