1. Buse DC, Sollars CM, Steiner TJ, Jensen RH, Al Jumah MA, Lipton RB (2012) Why HURT? A review of clinical instruments for headache management. Curr Pain Headache Rep 16(3):237–254
2. Costello AB, Osborne JW (2005) Best practices in exploratory factor analysis: four recommendations for getting the most from your analysis. Pract Assess Res Eval 10(7):1–9
3. Ertsey C, Magyar M, Csépány É, Kellermann I, Balogh E, Juhász N, Jánoska D, Palásti Á, Gyüre T, Bozsik G (2015a) Validation of the comprehensive headache-related quality of life questionnaire (CHQQ) in cluster headache: preliminary data. Cephalalgia 35(6S):85
4. Ertsey C, Csépány É, Manjunath NK, Vasudha MS, Jankovic S, Pakpour A, Srivastava A (2015b) The comprehensive headache-related quality of life questionnaire: status report. Cephalalgia 35(6):181–182
5. Fabrigar LR, Wegener DT, MacCallum RC, Strahan EJ (1999) Evaluating the use of exploratory factor analysis in psychological research. Psychol Methods 4(1):272–299