Older people 1,073 Organizational change 845 Operas 768 Organizational behavior 546 Organizational effectiveness 527 Operating systems (Computers) 482 Online social networks 363 Officials and employees 352 Organizational Innovation 327 Origin 327 Obesity 288 Orphans 259 Organization 233 Ontology 219 Open source software 211 Organizational learning 204 Opera 191 Organizational Culture 175 Organized crime 170 Officers 157 Organizational sociology 152 Orchestral music 150 Occupations 144 Organic compounds 142 Oral communication 140 Oral tradition 139 Objectivity 125 Occupational Health 116 Oral history 114 Outcome assessment (Medical care) 113 Occultism 107 Oceanography 100 Object Attachment 98 Organization and Administration 92 Occupational training 88 Oil spills 84 Oratory 83 Outlaws 83 Obsessive-compulsive disorder 81 Organizations 79 Obstetrics 76 Online journalism 74 Olympics 73 Obesity in children 72 Old age 68 Organic farming 66 Overtures 64 Orthopedics 63 Occupational therapy 62 Other (Philosophy) 61 Outcome Assessment, Health Care 61 Ojibwa Indians 60 Options (Finance) 60 Outcome and Process Assessment, Health Care 60 Observation (Educational method) 59 Optics 59 Opposition (Political science) 58 Orientalism 58 Ophthalmology 57 Object-oriented programming (Computer science) 56 Organisms 56 Orthodox Judaism 56 Occupational diseases 55 Orthopedic Procedures 54 Obsessive-Compulsive Disorder 52 Operations research 51 Orthodox Eastern Church 51 Occupational Therapy 50 Ocean 50 Operator theory 50 Occupational Exposure 48 Orthography and spelling 48 Oncology 46 Optical properties 46 Occupational Diseases 45 Older women 45 Outdoor education 45 Outdoor life 43 Ocean travel 42 Office management 42 Opioid abuse 42 Organizations, Nonprofit 42 Orthopedic surgery 42 Outdoor recreation 42 Ownership 41 Old age pensions 40 Otolaryngology 39 Object relations (Psychoanalysis) 38 Organ Transplantation 38 Operational readiness 36 Obituaries 35 Organizing 35 Other minds (Theory of knowledge) 35 Opioids 33 Optical communications 33 Optoelectronic devices 33 Oratorios 33 Operating systems 32 Oppression (Psychology) 32 Overpopulation 31