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:Sequencing reactions with Big Dye Taq premix were performed using forward primers of Cladosporium and Fusarium on an ABI 3130xl automated sequencer (Applied Biosystems) as described previously in Shipunov et al. (2008).
Category: