- Obersteiner, Heinrich, 1847-1922, author1
- Ohio. State Board of Health, author.1
- Osiander, Friedrich Benjamin, 1759-1822, author1
- Osler, William, Sir, 1849-1919, author1
- Owsiannikow, Ph., author1
- Owsjannikow, Philippus, 1827-1906 author1
- Owsjannikow, Philippus, 1827-1906, author2