Headland, T. N. (1986). Why foragers do not become farmers: A historical study of changing ecosystem and its effect on a Negrito hunter-gatherer group in the Philippines. UMI Dissertation Services.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रHeadland, Thomas N. Why Foragers Do Not Become Farmers: A Historical Study of Changing Ecosystem and Its Effect on a Negrito Hunter-gatherer Group in the Philippines. Ann Arbor, Mich: UMI Dissertation Services, 1986.
एमएलए (9वां संस्करण) प्रशस्ति पत्रHeadland, Thomas N. Why Foragers Do Not Become Farmers: A Historical Study of Changing Ecosystem and Its Effect on a Negrito Hunter-gatherer Group in the Philippines. UMI Dissertation Services, 1986.
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