| Author | Titles | | 1.
| Orr, Lynn Federle | 3 | | 2.
| Orr, Roger | 7 | | 3.
| Orrantia, Juan, 19--?- | 2 | | 4.
| Orrell, Paula | 2 | | 5.
| Orrick, Mildred, 1906-1994 | 1 | | 6.
| Orrit Willenberg-Giladi (Firma de Arquitectura) | 1 | | 7.
| Ors, Eugenio de, 1882-1954 | 8 | | 8.
| Ors Fuhrer, Carlos d' | 2 | | 9.
| Ors i Rovira, Eugeni d', 1882-1954 | 4 | | 10.
| Ors, Inés d' | 1 |
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