How about a works cited page (text file in your solution) and then comments in code files where the code is actually used. This gives you and the other developers some immediate context of where it came from, but the solution level text file provides an artifact in your software process.
The VB.NET XML comment ('''
) would allow for IntelliSense documentation as well, which may be overkill, but it would be available to developers at code implementation time.