(1991). Air pollution bigger threat to health and environment. Manila Times.
Chicago-referens (17:e uppl.)"Air Pollution Bigger Threat to Health and Environment." Manila Times 1991.
MLA-referens (9:e uppl.)"Air Pollution Bigger Threat to Health and Environment." Manila Times, 1991.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.