00262    a2200097   4500020001500000082001800015245004800033260004000081300001500121650002800136  a0335142818  a004.0151bOPE  aChapter 12 proofbBlock IV (Chapters 10-13)  aWaltonbOpen Universityc1995g1995  a52p.c29cm  aMathematical principles