00289nam a2200109Ia 4500082002600000100004000026245003200066260003400098300001000132500000500142700003200147  a309.10028542bD272.CG  aDawson, John A. and Unwin, David J.  aComputing for geographersb  aLondonbDavid & Charlesc1976  a362p.  a  aUnwin, David J. ; jt. auth.