Betts, R. B. (1985). In search of York: The slave who went to the Pacific with Lewis and Clark. Colorado Associated University Press.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Betts, Robert B. In Search of York: The Slave Who Went to the Pacific with Lewis and Clark. Boulder, Colo.: Colorado Associated University Press, 1985.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Betts, Robert B. In Search of York: The Slave Who Went to the Pacific with Lewis and Clark. Colorado Associated University Press, 1985.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.