00444nam a2200157Ia 4500008004100000082001800041100002300059245004400082260004600126300000800172650001400180650002000194653002100214653002700235700002400262170901s1949    xx            000 0 und d  a371.335bW25V  aWeaver, Gilbert G. 0aVisual AidsbTheir Construction and Use  aNew JerseybD. Van Nostrand Companyc1949  a388  aEducation  aSocial sciences  aAudiovisual aids  aEducational technology  aBollinger, Elroy W.