| Author | Titles | | 1.
| Orsulic, Marija | 1 | | 2.
| Orta, Garcia de, 1499?-1568 | 9 | | 3.
| Orta, Jorge, 1953- | 1 | | 4.
| Orta, Lucy | 1 | | 5.
| Ortega, Aaron Escobedo | 1 | | 6.
| Ortega, Ana Teresa, 1952- | 1 | | 7.
| Ortega, António, 19--?- | 1 | | 8.
| Ortega, Beatriz | 5 | | 9.
| Ortega, Carlos | 17 | | 10.
| Ortega Chapel, Pilar | 1 |
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