Non-working URL’s can be searched in http://archive.org .  I suspect that GPO uses non-working URL’s to search for archived federal websites such http://permanent.access.gpo.gov/lps126327/1993/mq23a935.txt 

Apologies if someone already pointed this out.

Thanks

Tim

Tim Watters

Special Materials Cataloger

Library of Michigan

702 West Kalamazoo St

P.O. Box 30007

Lansing, MI 48909-7507

Tel: 517-373-3071

e-mail: [log in to unmask]

-----Original Message-----

From: Program for Cooperative Cataloging [mailto:[log in to unmask]] On Behalf Of Steven C Shadle

Sent: Monday, May 21, 2012 5:04 PM

To: [log in to unmask]

Subject: Re: [PCCLIST] Question re invalid URLs in 856

Greta -- TBH, I have no idea why there are different practices or what the purpose was of leaving the non-working URL in 856|u …