Citation for the NRNSS: Cragun, R.T., Hammer, J.H., & Michael Nielsen, M. (2015). The nonreligious-nonspiritual scale (NRNSS): Measuring everyone from atheists to Zionists. Science, Religion, and Culture, 2(3), 36–53.
Science, Religion, and Culture is an open-access journal. You can download the article that describes the development and examination of the NRNSS directly from their site. Or you can download it here.
For those interested in using the scale, here are the items and directions for use.