- Operative techniques in thoracic and cardiovascular surgery
- Ophthalmic and physiological optics
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- Ophthalmology times
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- Optometry and vision science
- OR manager
- Oral and maxillofacial surgery cases
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- Oral science international
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- Orbis litterarum
- Orbit
- Organic letters
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- Organised sound
- Organisms, diversity & evolution
- Organization studies
- Organizational psychology review
- Organizational research methods
- Organometallics
- Origins of life and evolution of the biosphere
- ORNAC journal
- Ornithological applications / American Ornithological Society
- Ornithology
- Orthodontics and craniofacial research
- Orthopaedic proceedings
- Orthopaedics and trauma
- Orthopedic clinics of North America
- Orthopedic nursing
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- Oryx
- Osteoarthritis and cartilage
- Osteoporosis international
- OTJR : occupation, participation and health
- Otolaryngologic clinics of North America
- Otolaryngology case reports
- Otolaryngology--head and neck surgery
- Otology & neurotology
- Oxford journal of archaeology
- Pacific focus