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:‚Ä¶was observed at 18‚Äì24 ‚ó¶C, and similar results have been observed in G. tikvahiae McLachlan (Bird et al., 1979), G. chilensis (Laing et al., 1989 as G. sordida Nelson); Yokoya and Oliveira, 1992, Gracilaria sp. (chorda-type) (Chirapart et al., 1994), and G. vermiculophylla (Yokoya et al., 1999).
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