Nelson, Keith (December 1970). "The "Black Horror on the Rhine": Race as a Factor in Post-World War I Diplomacy". The Journal of Modern History. 42 (4): 611. doi:10.1086/244041. S2CID144070894.
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Nelson, Keith (December 1970). "The "Black Horror on the Rhine": Race as a Factor in Post-World War I Diplomacy". The Journal of Modern History. 42 (4): 611. doi:10.1086/244041. S2CID144070894.