McKenna SP, Doward LC. How should we measure quality of life in ankylosing spondylitis? Rheumatol Pract. 2008;6(2):12-4.
Gray-Little B, Williams VSL, Hancock TD. An item response theory analysis of the Rosenberg self-esteem scale. Pers Soc Psychol Bull. 1997;23(5):443-51. doi: 10.1177/0146167297235001