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:To generate transgenic Arabidopsis, constructs were mobilized into Agrobacterium tumefaciens strain AGL-1 using triparental mating, and transformed into Arabidopsis by vacuum infiltration as described in [39].
Category: