Improving the learning environment a study on the local preparation of visual instruction materials
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| 格式: | 图书 | 
| 语言: | English | 
| 出版: | 
        [Washington]
          U.S. Dept. of Health, Education, and Welfare, Office of Education
    
        [1963].
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| 丛编: | U.S. Office of Education. Circular no. 718
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