Okens Lehrbuch der Naturgeschichte - Oken, Lorenz, 1779 -1851 (Bei Carl Heinrich Reclam, 1816)

On a collection of birds from North-Eastern Abyssinia and the Bogos Country - Jesse, William. (Zoological Society of London, 1870)

On the anatomy of vertebrates - Owen, Richard, 1804 -1892 (Longmans, Green, 1866)

On the anatomy of vertebrates ... - Owen, Richard, 1804 -1892 (Longmans, Green and Co, 1866)

On the intestinal tract of birds; with remarks on the valuation and nomenclature of zoological characters - Mitchell, P. Chalmers Sir, (Peter Chalmers), 1864 -1945 (1901)

On the natural history and classification of birds - Swainson, William, 1789 -1855 (John Taylor, 1836)

On the Natural History and classification of Birds : vol. I and II - Swainson, William, 1789 -1855 (pr. for Longman [etc.], 1836)

Onomasticon zoicon, plerorumque animalium differentias & nomina propria pluribus linguis exponens : cui accedunt Mantissa anatomica, et quaedam De variis fossilium generibus - Charleton, Walter, 1619 -1707 (Apud Jacobum Allestry ..., 1668)

Ootheca Wolleyana: an illustrated catalogue of the collection of birds' eggs - Newton, Alfred, 1829 -1907 (sold by R. H. Porter, 1902)

Opera ornithologica - Bonaparte, Charles-Lucien, 1803 -1857 (1857)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1947)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1958)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1955)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1939)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1943)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1954)

The orchid hybrids. Second supplement - Hansen, Geo. (George), 1863 -1908 (Geo. Hansen, 1897)

The orchid hybrids enumeration and classification of all hybrids of orchids published up to October 15, 1895 - Hansen, Geo. (George), 1863 -1908 (Dulau, 1895)

The Orchid review (Orchid Review ltd.], 1894)

The Orchid review (Orchid Review ltd.], 1895)

The Orchid review (Orchid Review ltd.], 1900)

The orchid stud-book: an enumeration of hybrid orchids of artificial origin, with their parents, raisers, date of first flowering, references to descriptions and figures, and synonymy. With an historical introduction and 120 figures and a chapter on hybridising and raising orchids from seed - Rolfe, Robert Allen, 1855 -1921 (F. Leslie & co, 1909)

The orchid-stud book : an enumeration of hybrid orchids of artificial origin ... : with an historical introduction ... and a chapter on hybridising and raising orchids from seed - Hurst, C. C. 1870 -1947 (F. Leslie, 1909)

Orchids: their culture and management - Watson, William, 1858 -1925 (L. U. Gill, 1903)

L'Organisation du Règne animal. Oiseaux - Blanchard, Emile, 1819 -1900 (Chez l'Auteur)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1885)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1886)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1887)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1889)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1890)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1891)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1895)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1898)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1903)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1904)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1909)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1910)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1905)

Ornis Caucasica. Die Vogelwelt des Kaukasus : systematisch und biologisch-geographisch beschrieben - Radde, Gustav, 1831 -1903 (Verlag von Theodor Fischer, 1884)

Ornithologia methodice digesta, atque iconibus aeneis ad vivum illuminatis ornata - Lorenzi, Lorenzo. (In Aedibus Mouchianis, 1767)

Ornithologia methodice digesta, atque iconibus aeneis ad vivum illuminatis ornata - Lorenzi, Lorenzo. (In Aedibus Mouchianis, 1769)

Ornithologia methodice digesta, atque iconibus aeneis ad vivum illuminatis ornata - Lorenzi, Lorenzo. (In Aedibus Mouchianis, 1776)

Ornithologia, or, The birds: a poem, in two parts : with an introduction to their natural history; and copious notes - Jennings, James. (Sherwood, Gilbert, and Piper, 1829)

Ornithologia, sive, Synopsis methodica sistens avium divisionem in ordines, sectiones, genera, species, ipsarumque varietates : cum brevi & accurata cujusque speciei descriptione, citationibus auctorum de iis tractantium, nominibus eis ab ipsis impositis, nominibusque vulgaribus - Brisson, Mathurin-Jacques, 1723 -1806 (Apud Theodorum Haak, 1763)

Ornithologia Svecica - Nilsson, Sven, 1787 -1883 (Apud J.H. Schubothium, 1821)

Ornithological bibliography - Coues, Elliott, 1842 -1899 (Geological Survey [etc.], 1878)

Ornithological dictionary of British birds - Rennie, James, 1787 -1867 (Hurst, Chance, 1831)

Ornithological dictionary of British birds - Rennie, James, 1787 -1867 (W. S. Orr & W. Smith, 1833)

The ornithological guide - Wood, Charles Thorold. (Whittaker, 1835)

An ornithological index, arranged according to the synopsis avium of Mr. Vigors / by T. B. L. Baker - Vigors, N. A.‏ ‎ (Nicholas Aylward),‏ ‎ 1785 -1840 (Printed by R. Taylor, 1835)

Ornithological miscellany - Mintern Bros., (Trübner and Co., Bernard Quaritch, R.H. Porter, 1876)

[Ornithological papers] - Seebohm, Henry, 1832 -1895 (1876)

Ornithological rambles in Sussex : with a systematic catalogue of the birds of that county, and remarks on their local distribution / by A.E. Knox - Knox, Arthur Edward (J. Van Voorst, 1855)

The ornithological works of Arthur, ninth Marquis of Tweeddale - Wardlaw Ramsay, R. G. (Robert George), 1852 -1921 (Taylor and Francis, 1881)