Earth science : understanding environmental systems / Edgar W. Spencer. Spencer, Edgar Winston. Earth sciences. QE28 .S7 2003 550 21 SPE Includes index. Boston : McGraw-Hill, c2003. c2003. 2003 Text xxi, 518 p. : http://www.loc.gov/catdir/description/mh024/2002025073.html http://www.loc.gov/catdir/toc/mh023/2002025073.html eng