This site offers a scholarly, but also easy to read explanation of how to write good arguments.  Great step-by-step approach.

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This lesson from Purdue focuses on logic in argument.  The lesson is broken into the following subtopics:

• Logical Vocabulary
• Reaching Logical Conclusions
• Fallacies
• Improprieties

The site also includes exercises and links to other resources for students writin arguments.

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As usual, the Grammar Guide provides great, easy-to-understand explanations of writing skills.  The pages on writing arguments are excellent.  An example of a student-written argument with instructor commentary is provided.

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I think they cover every know logical fallacy on this site.  Each explanation of a logical fallacy also includes an example.  A great resource!

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