GTK+ and Glib documentation are available at http://gtk.org/api/, but a locally-installed set of documentation is preferable. If you installed GTK+ from SVN or a recent tarball (at the time this document was written, doing so is necessary for Epiphany SVN to compile), be sure to install the gtk-doc documentation along with it.

The author uses Devhelp for quick access to Glib and GTK+ documentation. There is some Epiphany documentation available, but it is not complete.

The GNOME Human Interface Guidelines: this documentation is not strictly required, but it should be treated with at least as much respect as exists towards the Bible, Koran, Torah and all other holy books.