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:Thus, searches can be conducted using Gene Symbols/Names, Keywords (partial terms such as casp for caspase), Keyword Symbols (partial symbols, such as erb for erbb2), OMIM ids (online mendelian inheritance in man [30]), diseases/disorders (such as diabetes), Tissue specificity (tissue expression patterns, such as genes expressed in muscle, derived from UniGene [31]), Gene Accessions, Protein Accessions, Entrez Gene IDs (from Entrez Gene [13]), UniGene Cluster IDs (from UniGene [31]), CDD Domain IDs (from conserved domain database [32]), Gene Ontology IDs (from Gene Ontology [9]), Definitions (from definition lines in GenBank [4]), HUGO IDs (from IDs defined by HUGO [5]), ENSEMBL IDs (from IDs defined by ENSEMBL [3]), SNPs (from dbSNP [33]) and Sequences (nucleic acid and protein sequences).
Category: