00349nam a2200121Ia 45000030006000000080041000060400015000471000026000622450081000882600029001695460012001980050017002100STCL150530s9999    xx            000 0 und d  aSTCLcSTCL  aByerly William Elwood  aIntroduction to the calculus of variations mathematical tracts for physicist  bHarward universityc1920  aEnglish20220125165950.0