00353nam a2200133Ia 45000030006000000080041000060400015000471000047000622450062001092500010001712600009001815460012001900050017002020STCL150530s9999    xx            000 0 und d  aSTCLcSTCL  aUniversity of Maryland Mathematics project  aUnifying concepts and processes in elementary mathematics  aFirst  c1978  aEnglish20220125170434.0