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:Next, backward and forward searches were performed for each relevant article, according to the guidelines provided by Levy and Ellis (2006) and Webster and Watson (2002). Backward searches included the sub-steps of backward references search, for example the work of Eng (2006) cited in Tomislav et al. (2014) and Chan and Chong (2013), backward authors search (e.
Category: