Sing to the Lord: Music in Divine Worship [87 pp. pdf] United States Conference of Catholic Bishops, November 14, 2007
(via Charlotte was Both)
Co-Workers in the Vineyard of the Lord: A Resource for Guiding the Development of Lay Ecclesial Ministry [70 pp. pdf] (2005) United States Conference of Catholic Bishops
Ethical and Religious Directives for Catholic Health Care Services, Fourth Edition, June 15, 2001, United States Conference of Catholic Bishops
General Instruction of the Roman Missal Including Adaptations for the Dioceses of the United States of America (2003), Committee on Divine Worship [also in pdf)
A Chronicle of the Reform: Catholic Music in the 20th Century, by Msgr. Richard J. Schuler; Cum Angelis Canere: Essays on Sacred Music and Pastoral Liturgy in Honour of Richard J. Schuler, Robert A. Skeris, ed., St. Paul MN: Catholic Church Music Associates, 1990, Appendix 6, pp. 349-419. Originally published in Sacred Music in seven parts.
The Catholic Encyclopedia (1917), at New Advent
Baltimore Catechism (1885), The Online Books Page