From https://web.archive.org/web/20220429090423/https://www.cgs.synth.net/
:
Ken Stone no longer maintains the Catgirl Synth (CGS - Ken Stone’s Modular Synthesizer) web site. The following resources will help you if you need to refer to any of the material.
Archival version of Catgirl Synth web site.
Catgirl Synth on Synth DIY wiki.
Last archived version on archive.org
(Generic CGS Search on archive.org. No valid pages after Aug 2018)
synthpanel.com appears to be defunct. The Synth DIY wiki site appears to have full copies of the CGS information, including the original images and verbatim text, though of course reformatted. The Elby Designs site I think also has the full original text, though for each module it’s divided between several linked pages, and at least some of Stone’s original schematics images are replaced with PDF outputs of EDA redraws. With these links Stone seemingly endorses both of the latter two sites.