1. Allen, M. P. (1976). Conventional and optimal interval scores for ordinal variables. Sociological Methods & Research, 4, 475–494.
2. Blalock, H. M., Jr. (1972). Social statistics (2nd ed.). New York: McGraw-Hill.
3. Burt, C. (1950). The factorial analysis of qualitative data. British Journal of Psychology, 3, 166–185.
4. Bӑltӑltescu, S. (2002, October). Problems of transforming scales of life satisfaction. Paper presented at Euromodule Workshop, Berlin.
5. Casacci, S., & Pareto, A. (2015). Methods for quantifying ordinal variables: A comparative study. Quality & Quantity, 49, 1859–1872. https://doi.org/10.1007/s11135-014-0063-2.