TY - JOUR T1 - Response to Hays et al and McHorney and Cohen: Practical implications of item response theory and computerized adaptive testing: A brief summary of ongoing studies of widely used headache impact scales JF - Medical Care Y1 - 2000 A1 - Ware, J. E., Jr. A1 - Bjorner, J. B. A1 - Kosinski, M. VL - 38 ER -