Modern Font Tech: FreeType2, libxft2, FontConfig

The design of FreeType 2
David Turner, The FreeType Development Team, 2000

FreeType Glyph Conventions
David Turner, The FreeType Development Team, 2000

The FreeType 2 Tutorial
David Turner, The FreeType Development Team, 2003

An Xft Tutorial
Keith Packard

The Xft Font Library: Architecture and Users Guide
Keith Packard, 2001

About Xft and Fontconfig
Keith Packard, Sep 2003.

FontConfig User Documentation (man 5 fonts-conf)

Fontconfig Developers Reference, Version 2.3.0
Keith Packard

Font Configuration and Customization for Open Source Systems
Keith Packard, 2002