Freedom and fellowship in religion: proceedings and papers of the Fourth International Congress of Religious Liberals, held at Boston, U.S.A., September 22-27, 1907
and much more.
Recommended Books
A great place to begin is this 'short list' of recommended books.
Reed, Rev. Clifford and Rev. Jill McAllister, eds. The Home We Share: Globalization, Post-Modernism and Unitarian/Universalist Theology—Proceedings of the 2nd ICUU Theological Symposium, Kolozsvár, Romania, July 3-8, 2006. Caerphilly, Wales: International Council of Unitarians and Universalists, 2007. Purchase through the UUA Bookstore