Orig, T. S. (1999). Photovoltaic (PV) technology can stop people from migrating to congested cities. Manila Bulletin.
Chicago-viite (17. p.)Orig, Thor S. "Photovoltaic (PV) Technology Can Stop People from Migrating to Congested Cities." Manila Bulletin 1999.
MLA-viite (9. p.)Orig, Thor S. "Photovoltaic (PV) Technology Can Stop People from Migrating to Congested Cities." Manila Bulletin, 1999.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.