Documentation of OpenType shaping behavior [for implementations]
https://github.com/n8willis/opentype-shaping-documents/
Indic text shaping for type designers
https://github.com/typotheque/text-shaping
OpenType specification
https://docs.microsoft.com/en-us/typography/opentype/spec/
TrueType Reference Manual
https://developer.apple.com/fonts/TrueType-Reference-Manual/
Annotated OpenType Specification
https://github.com/adobe-type-tools/aots
The Compact Font Format Specification
http://wwwimages.adobe.com/content/dam/Adobe/en/devnet/font/pdfs/5176.CFF.pdf
The Type 2 Charstring Format
http://wwwimages.adobe.com/www.adobe.com/content/dam/acom/en/devnet/font/pdfs/5177.Type2.pdf
Graphite
http://scripts.sil.org/cms/scripts/page.php?site_id=projects&item_id=graphite_home
Making Fonts for the Universal Shaping Engine
http://tiro.com/John/Universal_Shaping_Engine_TYPOLabs.pdf
OpenType is a registered trademark of Microsoft Corporation.
TrueType is a trademark of Apple Inc.