Ladd, G. T. (1914). What can I know?: An inquiry into truth, its nature, the means of its attainment, and its relations to the practical life. Longmans, Green.
Trích dẫn kiểu Chicago (xuất bản lần thứ 7)Ladd, George Trumbull. What Can I Know?: An Inquiry into Truth, Its Nature, the Means of Its Attainment, and Its Relations to the Practical Life. New York: Longmans, Green, 1914.
Trích dẫn kiểu MLA (xuất bản lần thứ 8)Ladd, George Trumbull. What Can I Know?: An Inquiry into Truth, Its Nature, the Means of Its Attainment, and Its Relations to the Practical Life. Longmans, Green, 1914.
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