ExpressionEngine includes a Trackback Module. There are two template tags that can be used with this module:
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You must have an ExpressionEngine license and have attained a forum rank of "Lab Assistant" (100 posts) to contribute notes to the User Guide
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User Contributed Notes
You must have an ExpressionEngine license and have attained a forum rank of "Lab Assistant" (100 posts) to contribute notes to the User Guide