Siringoringo, Panatar, Eka Daryanto, and Arif Rahman. 2017. “The Role of School Supervisors in Improving Vocational School (SMK) Accreditation in Humbang Hasundutan”. International Journal of Sciences: Basic and Applied Research (IJSBAR) 35 (3):160-65. https://www.gssrr.org/index.php/JournalOfBasicAndApplied/article/view/7985.