Springer, J. M. (1909). The heart of central Africa: Mineral wealth and missionary opportunity. Methodist Book Concern.
Chicago-viite (17. p.)Springer, John McKendree. The Heart of Central Africa: Mineral Wealth and Missionary Opportunity. New York: Methodist Book Concern, 1909.
MLA-viite (8. p.)Springer, John McKendree. The Heart of Central Africa: Mineral Wealth and Missionary Opportunity. Methodist Book Concern, 1909.
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