Item response theory for items scored in more than two categories
Citation
Thissen, D., Nelson, L., Rosa, K., & Mcleod, L.D. (2001).
Item response theory for items scored in more than two categories. In Thissen, D. & Wainer, H. (Eds.), Test Scoring (pp. 141-186). Mahwah, NJ: Lawrence Erlbaum Associates.