Lepar, Samuel Alexander, Rudy Poeng, and I Nyoman Gede. 2015. “ANALISIS RASIO KETEBALAN GERAM PADA PROSES PEMBUBUTAN”. JURNAL POROS TEKNIK MESIN UNSRAT 4 (2). https://ejournal.unsrat.ac.id/v3/index.php/poros/article/view/10461.