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:The most common advantages expressed in the six most-cited publications are that the flipped classroom approach focusses student-centred and collaborative, problem-based learning activities, thus enabling teachers to spend more time identifying student problems and knowledge gaps (Mason et al., 2013; McLaughlin et al., 2014; Prober & Khan, 2013; Strayer, 2012).
Category: