De ontwikkeling van het chondrocranium van Alytes obstetricans voor de metamorphose - Seters, Wouter Hendrik van. ("Het Klaverblad", 1921)

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, 1956)

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, 1957)

The origin and evolution of life : on the theory of action, reaction and interaction of energy - Osborn, Henry Fairfield, 1857 -1935 (Scribner's, 1918)

The origin and evolution of life, on the theory of action, reaction and interaction of energy - Osborn, Henry Fairfield, 1857 -1935 (C. Scribner's Sons, 1917)

The origin of the fittest : essays on evolution - Cope, E. D. (Edward Drinker), 1840 -1897 (D. Appleton, 1887)

The origin of the fittest : essays on evolution - Cope, E. D. (Edward Drinker), 1840 -1897 (Macmillan and Company, 1887)

The origin of the fittest; essays on evolution - Cope, E. D. (Edward Drinker), 1840 -1897 (D. Appleton, 1887)

Origin of the Greater Antillean land mammal fauna. 1, New Tertiary fossils from Cuba and Puerto Rico - MacPhee, R. D. E. (American Museum of Natural History, 1995)

Ornithological gazetteer of Uruguay - Paynter, Raymond A. Jr. (Obtainable from Bird Dept., Museum of Comparative Zoology, Harvard University, 1994)

Ornithological notes - Herrick, C. L. (Clarence Luther), 1858 -1904 (Geological and Natural History Survey of Minnesota, 1877)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1888)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1887)

Our common insects. A popular account of the insects of our fields, forests, gardens and houses - Packard, A. S. (Alpheus Spring), 1839 -1905 (Naturalists' Agency, 1873)

Our common insects A popular account of the insects of our fields, forests, gardens, and houses - Packard, A. S. (Alpheus Spring), 1839 -1905 (Estes and Lauriat, 1873)

Outlines of chordate development - Kellicott, William E. (William Erskine), 1878 -1919 (Holt, 1913)

Outlines of chordate development - Kellicott, William E. (William Erskine), 1878 -1919 (H. Holt and company, 1913)

Outlines of comparative anatomy of vertebrates - Kingsley, J. S. (John Sterling), 1854 -1929 (P. Blakiston, 1917)

Outlines of economic zoölogy - Reese, A. M. (Albert Moore), 1872 -1965 (P. Blakiston's Son & Co, 1919)

Outlines of general zoology - Baird, Spencer Fullerton, 1823 -1887 (Rudolph Garrigue, 1851)

Outlines of the comparative physiology and morphology of animals - LeConte, Joseph, 1823 -1901 (D. Appleton and company, 1900)

Outlines of vertebrate palæontology for students of zoology - Woodward, Arthur Smith, 1864 -1944 (University Press, 1898)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (Young J. Pentland, 1892)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (D. Appleton & Co, 1892)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (Young J. Pentland, 1895)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (D. Appleton & Co, 1895)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (Pentland, 1899)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (Appleton, 1916)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (H. Frowde and Hodder & Stoughton, 1899)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (D. Appleton, 1895)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (D. Appleton, 1906)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (H. Frowde and Hodder & Stoughton, 1921)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (Humphrey Milford, Oxford University Press, 1929)

Over de ontwikkeling van het chondrocranium en de kraakbeenige wervelkolom van eenige Urodela en Anura - Peeters, Johannes Leonardis Elbertus. (G.F. Theonville, 1910)