Ocherki istorii arabskoj kultury 5-15 vv.(1982).Nauka(Moscow). pps 360, 364, 387, 392, 396,407. In Russian [1159]

O'Shea, B. (1995). Checklist of mosses of sub-Saharan Africa. See pp 98, 99-100, 114, 144, 151. Tropical Bryology 10: 91-198.[711]

Ogilvie-Grant, W.R. and Forbes, H.O (1899). The Expedition to Sokotra. 1. Descriptions of the new species of birds. Bulletin of the Liverpool Museums 2(1): 2-3.[716]

Ogilvie-Grant, W.R. and Forbes, H.O (1903). Choradata. Vertebrata. Aves. Birds 21-22. I. The birds of Sokotra: 23-57. 2 figures; 13 musical notations of bird calls; 2 drawings from paintings by artist P.J. Smit. II. Birds of Abd-el-Kuri: 58-63. Colour Plate III - Fringillaria socotrana; Fringillaria insularis; artist H. Gronvold. Colour Plate IV - Caprimulgus jonesi; artist H.Gronvold. Colour Plate V - Scops socotranus; artist H.Gronvold. Colour Plate VI - Phalacrocorax nigrogularis; artist H. Gronvold. Colour Plate VII - Passer hemi leucus; Motacilla forwardi; artist H.Gronvold. In Natural history of Sokotra and Abd-el-Kuri, Editor: H.O. Forbes. Bulletin of the Liverpool Museums (Special Bulletin): 19-72.[717]

Ogilvie-Grant, W.R. (1899). The Expedition to Sokotra. IV Descriptions of three new species of butterflies. Bulletin of the Liverpool Museums 2(1): 10-11.[712]

Ogilvie-Grant, W.R. (1903). Arthropoda. Insecta: Lepidoptera - I. Rhopalocera. Butterflies: 295. I. The butterflies of Sokotra: 295-313. II. The butterflies of Abd-el-Kuri: 314. Colour Plate XVIII - Butterflies from Sokotra. Depicts Charaxes velox; artist M. Horman-Fisher. Colour Plate XIX - Butterflies from Sokotra. Depicts Charaxes balfouri, Tarucus socotranus, Tarucus quadratus, belenois anomala, Rhopalocampta jucunda; artist M. Horman-Fisher. In Natural history of Sokotra and Abd-el-Kuri, Editor: H.O. Forbes.[713]

Ogilvie-Grant, W.R. (1913). Exhibition and description of a new subspecies of Grosbeak, Rhynchostruthus percivali yemenensis, from the mountains of S. Yemen. Bulletin of the British Ornithologists' Club 31(189): 112-113.[714]

Ogilvie-Grant, W.R. (1914). Report of a new race of Palm Dove. Bulletin of the British Ornithologists' Club 35: 19.[715]

Oldfield, Sara (1993). International trade in Aloes. Traffic Bulletin 14(1): 25-32.[718]

Orr, N.W.M. and Lister, R.L. (1958). Medical Report. Oxford University Expedition to Socotra, 1956. Typescript. pp 17. Coral Gables, Florida: Miscellanea Asiatica Orientalis Series. American Documentation Institute Microfilm (ADIM) No. 5624. Washington D.C.: Library of Congress.[719]

Owen, Captain W.F.W. (1833). Narrative of voyages to explore the shores of Africa, Arabia, and Madagascar; performed in H.M. Ships Leven and Barracouta, under the direction of Captain W.F.W. Owen, R.N. by command of the Lords Commissioners of the Admiralty. Two Volumes. (Volume II, pp 350-352, deals with a hydrographic survey of socotra and the adjacent islands). London: Richard Bentley.[720]