Thissen D, Nelson K, Rosa K, McLeod L. Item response theory for items scored in more than two categories. In: Thissen D, Wainer H, editors. Test scoring. Hillsdale: NJ. Lawrence Erlbaum Associates Publishers; 2001.
McLeod LD, Swygert KA, Thissen D. Factor analysis for items scored in two categories. In: Thissen D, Wainer H, editors. Test scoring. Hillsdale: NJ. Lawrence Erlbaum Associates Publishers; 2001.
Swygert KA, McLeod L, Thissen D. Factor analysis for items or testlets scored in more than two categories. In: Thissen D, Wainer H, editors. Test scoring. Hillsdale: NJ. Lawrence Erlbaum Associates Publishers; 2001.