Hi all. I'm somewhat surprised that I've never had to validate an ISBN manually up until now. I suppose that's a testiment to all of the software out there. However, I now find that I need to validate both the 10-digit and 13-digit ISBNs. I realize there's also a check digit and a REGEX cannot check this value - one step at a time. Right now I just want to work on the REGEX. Does anyone know the exact specifications of both forms of an ISBN? The ISBN organization's website didn't seem to be overly clear to me. Alternatively, if anyone has a full working regular expression for this purpose I would definitely not mind if they'd be willing to share. The only thing I'm doing which is abnormal is that I am not requiring the hyphenation or spaces between numbers since some of this data will be coming from a system, and some will be coming from human input. Brendon Kozlowski Web Administrator Saratoga Springs Public Library 49 Henry Street Saratoga Springs, NY, 12866  584-7860 x217 Please consider the environment before printing this message. To report this message as spam, offensive, or if you feel you have received this in error, please send e-mail to [log in to unmask] including the entire contents and subject of the message. It will be reviewed by staff and acted upon appropriately.