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Source Code Repositories
See Version control.
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Annotation Tools
Cool Collaborative PDF annotation tool : http://nb.mit.edu !
Course Forums
Piazza is an online forum environment designed specifically for courses. It provides very rich control over registration (open or closed), student vs. instructor capabilities, web and email notifications, mobile apps, searching, tagging, response editing, and statistics. It takes only a few minutes for an instructor to set up a Piazza forum for a course.
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