Harvard African Expedition & Strong, R. P. (1930). The African republic of Liberia and the Belgian Congo: Based on the observations made and material collected during the Harvard African Expedition, 1926-1927. Harvard University Press.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Harvard African Expedition و Richard Pearson Strong. The African Republic of Liberia and the Belgian Congo: Based on the Observations Made and Material Collected During the Harvard African Expedition, 1926-1927. Cambridge [Mass.]: Harvard University Press, 1930.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Harvard African Expedition و Richard Pearson Strong. The African Republic of Liberia and the Belgian Congo: Based on the Observations Made and Material Collected During the Harvard African Expedition, 1926-1927. Harvard University Press, 1930.