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.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Headland, 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.
توثيق جمعية اللغة المعاصرة MLA (الإصدار التاسع)Headland, 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.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.