Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:…dual tasking adversely affects multiple aspects of gait in patients with PD and in older adult idiopathic fallers (i.e., those elderly who fall without any clear reason) (Bond and Morris 2000; Camicioli et al. 1998; O’Shea et al. 2002; Yogev et al. 2005; Springer et al. 2006; Bloem et al. 2001).
Category: