Waller, N. G., Kojetin, B. A., Bouchard, T. J., Lykken, D. T., & al., et. (1990). Genetic and environmental influences on religious interests, attitudes, and values: a study of twins reared apart and together. Psychological Science, 1(2), 138–142. http://www.blackwellpublishers.co.uk/asp/journal.asp?ref=0956-7976