Não informado. Philippine Journal of Soils. Department of Agriculture and Natural Resources.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Philippine Journal of Soils. Manila: Department of Agriculture and Natural Resources.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Philippine Journal of Soils. Department of Agriculture and Natural Resources.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.