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:Regarding camera sensors, the work of Jung et al (2014) explores information from a depthcamera, while a monocular camera is employed in (Wu et al 2009; Costante et al 2013), and an omnidirectional one in (Ullah et al 2008; Yuan et al 2011).
Category: