Transforming the National Department of Veterans Affairs Data Warehouse to the OMOP Common Data Model. - Fern FitzHenry; Jesse Brannen; Jason N. Denton; Jonathan R. Nebeker; Scott L. DuVall; Freneka F. Minter; Jeffrey Scehnet; Brian C. Sauer; Lucila Ohno-Machado; Michael E. Matheny (AMIA, 2015)