Eclipse version 3.6.1: where might jar names be referenced other than .classpath file?

I am seeing the following error in the "Problems" view of my java project:

Pr开发者_StackOverflowoject 'foo' is missing required library: 'lib/tapestry-archetype-4.1.6.jar'

This jar is not referenced in my project's classpath file (although it was there previously), so I'm not sure where this error is coming from. Is this information cached somewhere in Eclipse? If so, how do I clear the cache?

Thanks, Jonathan

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Check the project's Properties > Java Build Path > Libraries.

I'm not sure how Eclipse will handle things if you edit the .classpath file of a project that is already open; Eclipse may not expect in-place edits of the metadata files to occur.