PostScript Language Reference Manual, Adobe Systems. - 2nd ed. ISBN 0-201-18127-4 - defines PostScript language and fonts
PostScript Language Extension for CID-Keyed Fonts. PostScriptTMSoftware Version 2015 Adobe Systems 29 June 1995
The Type 42 Font Format Specification. Adobe Systems Technical Note #5012 1 March 1993
Fontadmin Functional Specification - 12/04/95 - documents font downloader
TrueType Font File Version 1.00 Microsoft Corporation --available from ftp.microsoft.com - documents TrueType fonts