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