Links between Gene and PubMed are the result of the following: 1. Manual curation within NCBI. Part of the process of generating a REVIEWED RefSeq is an analysis of the current literature. Papers that are seminal in defining the gene, its sequence, and its function are added to the record at that time. Alert users point out gaps or errors in papers associated with a Gene record. These messages are reviewed and implemented as required. 2. Integration of information from other public databases. Gene integrates gene-citation from resources external to NCBI such as model organism-specific databases, Gene Ontology (GO), groups curating interactions, and sequence databases. The assumption in using these source is that they report citations specific to a gene in a known species. Gene does not process citations from OMIM automatically, because many of citations in OMIM refer to studies of genes in species other than human.