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:…an enormous diversity of anamorphic fungi growing on rotten wood and dead branches in tropical forests of southern China, and several mycological investigations dealing with many new species collected in this region have recently been published (Yuan&Dai 2008; Zhang et al. 2009; Dai et al. 2009).
Category: