| Author | Titles | 1.
| O'Neill, Rosemary | 2 | 2.
| O'Neill, Timothy | 1 | 3.
| O'Neill-Butler, Lauren | 1 | 4.
| Öney, Gönül | 1 | 5.
| Onfray, Michel, 1959- | 3 | 6.
| Ongania, F., 1842-1911 | 0 | 7.
| Author is: Ongania, Ferdinando, 1842-1911 | 1 | 8.
| Ongania, Ferdinando, 1842-1911 | 1 | 9.
| ONGD Plataforma Portuguesa | 1 | 10.
| Onians, John, 1942- | 3 | 11.
| ONICIU, A.P. | 1 |
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