OSTREA, Enrique.
 The Surigao Iron Ore and Its Metallurgical Treatment.
<strong>Philippine Engineering Journal</strong>, [S.l.], v. 31, n. 1, aug. 2021.
ISSN 2718-9287.
Available at: &lt;<a href="https://journals.upd.edu.ph/index.php/pej/article/view/7932" target="_new">https://journals.upd.edu.ph/index.php/pej/article/view/7932</a>&gt;. Date accessed: 05 sep. 2025.