Walker, R. (2011). What is the theory of evolution? Crabtree Pub..
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रWalker, Robert. What Is the Theory of Evolution? New York, N.Y.: Crabtree Pub., 2011.
एमएलए (8वां संस्करण) प्रशस्ति पत्रWalker, Robert. What Is the Theory of Evolution? Crabtree Pub., 2011.
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