00301nam a2200097Ia 4500008004100000082001900041100001800060245008600078260003300164300000600197260907b        |||||||| |||| 00| 0 eng d  a510.9bP781.MD  aPolya, George  aMathematical discovery on understanding, learning and teaching problem solvingb/  aNew York:bJohn Wiley,c1962  a