Display All Unauthorized Music???

Is there I trick that I haven't found to be able to quickly and easily seach & display all unauthorized music in my iTunes? I have 20,000 songs amassed from a variety of sources and want to delete all unauthorized music at one time rather than waiting until I try to play it to delete them one at a time.
Thanks all-
Jeff

Finally found something that worked great! For those interested here is a link to it. When you run it, a playlist is created for every account that has purchased music (that exists in your iTunes library) such as: "Bill Smith's Purchased Music", "Jim Johnson's Purchased Music", etc. Thanks anyway.
Blue skies-
Jeff

Doug's AppleScripts for iTunes ♫ Track Down Purchases v1.0