* Technical – The books must be nonfiction and provide in-depth information on a particular subject
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** Good: Transformers and Motors
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** Bad: Harry Potter and the Philosopher's Stone
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* Useful – The books must pertain to something people in the space are doing or are interested in, and the information is not readily available online.
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** Good: Hand-Manipulated Stitches for Machine Knitters
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** Bad: German to French dictionary
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* Current – The books must provide information that is still at least mostly true.
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* In Good Condition
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==Resources==
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* For K-12 textbooks: http://www.ck12.org/student/
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* Directory of Open Access Journals: http://www.doaj.org/