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:Using this strategy, we generated HA-tagged chimeras encoding the N-terminal domain of PR NS1 fused to the C terminus of Tx NS1 [PR(1-80)Tx(81-230)] and vice versa [Tx(180)PR(81-230)].
Category: