Dyfyniad APA

World Book, Inc. (2007). The Skeletal system, the muscular system. World Book.

Dyfyniad Arddull Chicago

World Book, Inc. The Skeletal System, the Muscular System. Chicago: World Book, 2007.

Dyfyniad MLA

World Book, Inc. The Skeletal System, the Muscular System. World Book, 2007.

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