(1999). World population hits 6 billion today. Philippine Daily Inquirer.
Cita Chicago (17th ed.)"World Population Hits 6 Billion Today." Philippine Daily Inquirer 1999.
Cita MLA (9th ed.)"World Population Hits 6 Billion Today." Philippine Daily Inquirer, 1999.
Atenció: Aquestes cites poden no estar 100% correctes.