| Author | Titles | | 1.
| Horta, Rui, 1957- | 1 | | 2.
| Horta, Vera de | 1 | | 3.
| Horta, Victor, 1861-1947 | 5 | | 4.
| Hortalà, Lluís, 1959- | 1 | | 5.
| Horticultural Society of London (Londres, Grã-Bretanha) | 0 | | 6.
| Author is: Royal Horticultural Society (Londres, Grã-Bretanha) | 2 | | 7.
| Hortolà, Josep | 5 | | 8.
| Horton, Charles | 2 | | 9.
| Horton, Kristan, 1971- | 1 | | 10.
| Horton, W. Claude | 1 | | 11.
| Hortus Regius Botanicus Kewensisrdens (Grã-Bretanha) | 0 | | 12.
| Author is: Grã-Bretanha. Royal Botanic Gardens (Kew) | 2 |
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