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:Whole mount in situ hybridization using digoxigenin-labeled RNA probes was performed as described [61]. cDNA probes used for in situ hybridization were as described previously: Brachyury [23], Foxa2/HNF3Œ≤ [26], Hesx1 [62], Lhx1 [27], Otx2 [28], and Bmp4 [29].
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