1. KEGG: Kyoto Encyclopedia of Genes and Genomes,
http://www.genome.jp/kegg/
2. NCBI Taxonomy Database,
http://www.ncbi.nlm.nih.gov/Taxonomy/
3. PostgreSQL,
http://postgresql.org
4. The Gene Ontology,
http://www.geneontology.org/
5. The Pfam Protein Families Database,
http://pfam.sanger.ac.uk