Donald A. Luidens, professor of sociology at Hope College in Holland, Mich. (affiliated with the Reformed Church in America), has followed the evolution of denominations and denominationalism in the U.S.

Darren E. Sherkat is a professor of sociology at Southern Illinois University at Carbondale. He studies the intersection of religion, family and politics, and he’s working on a book about marijuana legalization.

Daniel V. A. Olson, associate professor of sociology at Purdue Univeristy. Specializes in sociology of religion and has written about church growth.

Daniel Montgomery founded and serves as the lead pastor for Sojourn Community Church in Louisville, Ky., a church plant. Sojourn began as an attempt to reach people who were falling through the cracks in more mainstream churches. It officially launched in September 2000 using rented space and has expanded to include multiple campuses.

The American Religion Data Archive lists Pentecostal denominations (scroll down to U.S. Denominations). Some scholars have named more than 300.

Mark Perakh is a professor emeritus of physics at California State University, Fullerton. He is author of Unintelligent Design (Prometheus Books, 2004).

See a timeline of the Azusa Street revival.

John Schneeberger is with the Bitterroot Human Alliance in Hamilton, Mont., and advocated against the inclusion of intelligent design in Darby public schools.

The Encyclopedia of Religion and Society entry on Pentecostalism gives an overview of the history and issues facing Pentecostalism.