David A. Harris is executive director of the American Jewish Committee, a nonpartisan organization that conducts an annual survey of American Jews.

Tamar Ross is a professor of Jewish philosophy at Bar-Ilan University in Ramat Gan, Israel. She writes about Orthodoxy and feminism.

Daniel Frank is director of the Judaic studies program at Purdue University in West Lafayette, Ind.

Read a Feb. 11, 2009, CBS News story on Hasidic reggae singer Matisyahu.

Read an essay on the history of Orthodox Judaism in America adapted from the American Jewish Desk Reference: The Ultimate One Volume Reference to the Jewish Experience in America and posted at the MyJewishLearning.com Web site.

Read an essay by Michael Kress, editor in chief of MyJewishLearning.com, about the factions and tensions within the Orthodox movement.

The Berman Jewish DataBank has links to the National Jewish Population Study and several other studies, some of which provide different figures for the overall Jewish population.

Read the National Jewish Population Survey’s reports on geographic differences among Jews around America. The NJPS showed that although the Orthodox influence is felt nationally, Orthodox Jews are concentrated in urban Northeast areas to a greater degree than other Jews.

Eliezer Segal, a professor of religious studies at the University of Calgary, has a Web page explaining the “Varieties of Orthodox Judaism.” The page sets out the many branches of the movement.