File:High School Earth Science 1-13.pdfDescriptionHigh School Earth Science 1-13.pdf English: The first source PDF for the High School Earth Science Wikibook. Date 22 February 2010 Source http://about
File:CK12 Earth Science.pdfDescriptionCK12 Earth Science.pdf English: Earth Science book from the CK-12 Foundation. Date 11 June 2009 Source CK-12 Foundation at www.ck12.org (See