Payawal, P. C., Esmundo, R. R., & Pagulayan, R. C. (1999). Life and the planet earth. Learning Resource Center, University of the Philippines.
Citazione stile Chigago Style (17a edizione)Payawal, Pacifico C., Rosalinda R. Esmundo, e Roberto C. Pagulayan. Life and the Planet Earth. Diliman, Quezon City: Learning Resource Center, University of the Philippines, 1999.
Citatione MLA (9a ed.)Payawal, Pacifico C., et al. Life and the Planet Earth. Learning Resource Center, University of the Philippines, 1999.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.