Hypertext Book of Hours: site by Glenn Gunhouse with English and Latin texts from a Book of Hours, c. 1599
www.medievalist.net/hourstxt/home.htm

The Center for Handskriftstudier i Danmark, introduction and tutorial on Books of Hours by Erik Drigsdahl
www.chd.dk/tutor/index.html

On Use: selective collection of incipits from the Hours of the Virgin
www.chd.dk/use/index.html

On-line Calendar of Saints Days
http://www.medievalist.net/calendar/home.htm

The Pierpont Morgan Library manuscripts
www.corsair.morganlibrary.org

Bohatta, Bibliographie des Livres d’Heures des XV & XVI Jahrhunderts, Vienna, 1924 (on printed Books of Hours)
www.rarebooks.info