Postrado, L. D. Firm mining in Bicol questioned. IN Luzon News. Manila Bulletin.
Cita Chicago (17th ed.)Postrado, Leonard D. "Firm Mining in Bicol Questioned. IN Luzon News." Manila Bulletin .
Cita MLA (9th ed.)Postrado, Leonard D. "Firm Mining in Bicol Questioned. IN Luzon News." Manila Bulletin, .
Atenció: Aquestes cites poden no estar 100% correctes.