Csima, Barbara F. Max Planck Institute for Mathematics, Max Planck Society;
https://doi.org/10.1215/00294527-1960479 (Publisher version)
Csima, B. F., Franklin, J. N. Y., & Shore, R. A. (2013). Degrees of categoricity and the hyperarithmetic hierarchy. Notre Dame Journal of Formal Logic, 54(2), 215-231. doi:10.1215/00294527-1960479.