| Author | Titles | 1.
| Oropesa, Marisa | 3 | 2.
| Oropreto, Isaac d'Espiney | 1 | 3.
| O'Rourke, Isella Fiale | 1 | 4.
| O'Rourke, Karen | 1 | 5.
| O'Rourke, Meg | 1 | 6.
| Oroveanu, Anca | 1 | 7.
| Oroz, Jose | 1 | 8.
| Orozco Díaz, Emilio | 2 | 9.
| Orozco, Gabriel, 1962- | 15 | 10.
| Orozco, José Clemente, 1883-1949 | 1 |
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