Dear Justin:

You can find reference to GDS II format in:

CAD for VLSI Design
by: Steve Rubin
Addison Wesley 1987; pg. 349-356.

We also have more info internally. If you have specific question, let us know.
Good luck.

Fariborz Maseeh
IntelliSense Corporation
16 Upton Drive
Wilmington, MA 01887
(508) 988 - 8000
(508) 988 - 8001 fax