BORLAGDAN, Paterno C..
 Design and Development of a Two Post Rotary-Percussion Drilling Rig.
<strong>Philippine Engineering Journal</strong>, [S.l.], v. 16, n. 1, sep. 2021.
ISSN 2718-9287.
Available at: &lt;<a href="https://journals.upd.edu.ph/index.php/pej/article/view/8062" target="_new">https://journals.upd.edu.ph/index.php/pej/article/view/8062</a>&gt;. Date accessed: 09 sep. 2025.