- Pre-release specification: https://web.archive.org/web/20060911215716/http://chs75.harvard.edu/projects/diginc/techpub/registry (Wayback Machine, 2006)
- No longer available as of 2013
- D. Neel Smith
From the specification page (preserved 2006-09-11):
Motivation: Registry Services differ from other automated authority lists providing a recursive, hierarchical classification schemes of any depth, and in requiring that all entries in a registry include an attestation in a standard reference scheme for each entry in the registry.
- Smith, N. Registry Services, Digital Incunabula pre-release - development version (19 August 2005): http://chs75.harvard.edu/projects/diginc/techpub/registry.