Observationes entomologicae, continentes novorum quae condidit generum characteres, et nuper detectarum specierum descriptiones - Weber, Friedrich, 1781 -1823 (impensis Bibliopolii Academici Novi, 1801)

Observationes Zoologicae : quibus novae complures, aliaeque animalium species describuntur et illustrantur - Hermann, Johannis. (Amandum Koenig, 1804)

Occasional papers of the Boston Society of Natural History - Boston Society of Natural History. (Boston Society of Natural History, 1869)

The Odonata or dragonflies of South Africa - Ris, F. (Friedrich), 1867 -1931 (Printed for the Trustees of the South African Museum by Adlard, 1921)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1863)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1892)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1906)

Oeuvres entomologiques de Eschscholtz Tome 1 Entomographien - Eschscholtz, Johann Friedrich, 1793 -1831 (Lequien Fils, 1835)

Öfversigt af Finska vetenskaps-societetens förhandlingar - Suomen Tiedeseura (s.n.], 1912)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1844)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1867)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1869)

Olivier's Entomologie oder Naturgeschichte der Insekten mit ihren Gattungs- und ArtMerkmalen, ihrer Beschreibung und Synonymie Käfer - Sturm, Jakob, 1771 -1848 (Gedrukkt und im Verlage bei Karl Reichard, 1800)

Om Sveriges hydrachnider - Neuman, Carl Julius, 1839 -1912 (Kongl. boktryckeriet, P.A. Norstedt & söner, 1880)

On animal and vegetable parasites of the human body a manual of their natural history, diagnosis, and treatment - Lankester, Edwin, 1814 -1874 (Printed for the Sydenham Society, 1857)

On animal and vegetable parasites of the human body, a manual of their natural history, diagnosis, and treatment - Küchenmeister, Friedrich, 1821 -1890 (Printed for the Sydenham Society, 1857)

On the Chilopoda of North America, with a catalogue of all the specimens in the collection of the Smithsonian Institution - Academy of Natural Sciences of Philadelphia. (Academy of Natural Sciences of Philadelphia, 1862)

On the Paussidae, a family of coleopterous insects - Westwood, J. O. (John Obadiah), 1805 -1893 (1833)

On two orders of Arachnida : Opiliones, especially the suborder Cyphophthalmi, and Ricinulei, namely the family Cryptostemmatoidae - Royal Society (Great Britain) (University Press, 1904)

Opuscules entomologiques - Mulsant, Martial Étienne, 1797 -1880 (L. Maison, 1853)

Orchidaceae: illustrations and studies of the family Orchidaceae - Ames, Oakes, 1874 -1950 (Houghton, Mifflin, 1910)

Otia botanica Hamburgensia :Fasciculus primus [-secundus, pars prima] - Reichenbach, H. G. (Heinrich Gustav) 1824 -1889 (Typis T. T. Meissneri, 1878)

Ouresiphoitēs Helveticus, sive, Itinera per Helvetiae Alpinas regiones facta annis MDCCII, MDCCIII, MDCCIV, MDCCV, MDCCVI, MDCCVII, MDCCIX, MDCCX, MDCCXI : plurimis tabulis aeneis illustrata - Scheuchzer, Johann Jakob, 1672 -1733 (Typis ac sumptibus Petri Vander Aa, 1723)

Oversigt over det Kongelige Danske videnskabernes selskabs forhandlinger = Bulletin de l'Académie royale des sciences et des lettres de Danemark - Kongelige Danske videnskabernes selskab. (A.F. Høst, 1891)

P.A. Latreille scientiarum et artium instituti Gallici ... Genera crustaceorum et insectorum : secundum ordinem naturalem in familias disposita, iconibus exemplisque plurimis explicata - Latreille, P. A. (Pierre André), 1762 -1833 (Apud Amand Knig, Bibliopolam, 1806)

P.A. Latreille scientiarum et artium instituti Gallici ... Genera crustaceorum et insectorum : secundum ordinem naturalem in familias disposita, iconibus exemplisque plurimis explicata - Latreille, P. A. (Pierre André), 1762 -1833 (Apud Amand Knig, Bibliopolam, 1807)