00454nam a2200157 a 450000500170000000800410001702000180005805000230007610000180009924500510011725000160016826000550018430000170023944000200025665000200027620140412111250.0000901s19uu    xx            00    eng d  a0-8136-7297-X  aBB 551.7bW34 1993  aWalker, Colin  aOur changing earth /cwritten by Colin Walker.  a2nd Edition  aCelveland, Ohio :bModern Curriculum Press,c1993.  a17 p. ; ill.  aConcept Science  aSciencesxEarth