00274nam a2200109Ia 4500008004100000100002800041245002100069250001200090260004200102300000800144650001200152190216s9999||||xx |||||||||||||| ||und||  aNelkon. M  A Nd Inst. P 0aLight And  Sound  a3rd Ed.  bHeinemann Educational Books Ltdc1966  a420  aPhysics