01168nam0-2200361-i-450-99000928118040332120101117122947.0000928118FED01000928118(Aleph)000928118FED0100092811820101117d1997----km-y0itay50------baengFIa---a---101yyProceedings of the 21st conference of the international group for the Psychology of Mathematics Educationedited by Erkki PehkonenHelsinkiUniversity of Helsinki19974 v.21 cmPsychology of mathematics education21Educazione matematica372.721itaPehkonen,ErkkiITUNINAREICATUNIMARCBK990009281180403321CPDM-97-092-(19MA1CPDM-97-092-(210MA1CPDM-97-092-(311MA1CPDM-97-092-(412MA1MA197-XXProceedings of the 21st conference of the international group for the Psychology of Mathematics Education769462UNINA