APA

national geographic society, . (2001). Earth & Physical Sciences. new york: Mcgraw - hill.

Chicago

national geographic society, . 2001. Earth & Physical Sciences. new york: Mcgraw - hill.

Harvard

national geographic society, . (2001). Earth & Physical Sciences. new york: Mcgraw - hill.

MLA

national geographic society, . Earth & Physical Sciences. new york: Mcgraw - hill. 2001.