Rorvig, M. (2000). A New Method of Measurement for Question Difficulty.
Citazione stile Chigago Style (17a edizione)Rorvig, Mark. A New Method of Measurement for Question Difficulty. 2000.
Citatione MLA (9a ed.)Rorvig, Mark. A New Method of Measurement for Question Difficulty. 2000.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.