1991 Manpower factbook. Research and Evaluation Division of the Office of Manpower Planning and Coordination.
Cita Chicago (17th ed.)1991 Manpower Factbook. Metro Manila: Research and Evaluation Division of the Office of Manpower Planning and Coordination.
Cita MLA (9th ed.)1991 Manpower Factbook. Research and Evaluation Division of the Office of Manpower Planning and Coordination.
Atenció: Aquestes cites poden no estar 100% correctes.