Obra, B. Q., Villanueva, A. F. R., & Miranda, F. E. (1982). Mineral resources in the coastal area of Region I. Bureau of Mines and Geo-Sciences.
Citazione stile Chigago Style (17a edizione)Obra, Benjamin Q., Abner Fe R. Villanueva, e Federico E. Miranda. Mineral Resources in the Coastal Area of Region I. Baguio City: Bureau of Mines and Geo-Sciences, 1982.
Citatione MLA (9a ed.)Obra, Benjamin Q., et al. Mineral Resources in the Coastal Area of Region I. Bureau of Mines and Geo-Sciences, 1982.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.