00500nam a2200157Ia 450000500170000000800460001703700120006304000210007504100130009608400210010924500530013024500480018326000750023130000100030654600260031620250508161722.0008  250505s9999    xx            000 0 eng d  aTextual  aFEDL bengcFEDL  aeng2eng  a510.7, NATqFEDL 0aLearning of mathematics: Its theory and practice 0cNational Council of Teachers of Mathematics  aWashington, USAbThe National Council of Teachers of Mathematicsc1953  a355p.  aTwenty-first yearbook