The relationship of internal and external pages, and an example of using the CEG database. A, home page; B, search page; C, D, and E, browse pages. A to E are the internal pages of the CEG database, and these are surrounded by a blue dashed line. F to I are external pages, and are surrounded by a green dashed line. F, DEG database; G, HPRD database; H, NCBI database; I, KO database.