The New Westminster Dictionary of Liturgy and Worship
Religious Studies and Philosophy (Non-Circulating) BT 4009 .D25 D5 2002
Dictionnaire d'Archéologie Chrétienne et de Liturgie
Religious Studies and Philosophy (Non-Circulating) BX 57 .C3
With the exception of Book 14 part 1 and Book 15, this set is available online from the Internet Archive and The National Library of France:
Notitiae (online) - Periodical of the Congregation for Divine Worship and the Discipline of the Sacraments (CDWDS)
New Liturgical Movement / Novus Motus Liturgicus (online) - Contains recent news and articles, information about liturgical studies books, liturgical books, conference proceedings, organizations, lay societies, and many other resources.