World Health Organization 61 Series 16 Guidelines 13 Risk assessment 10 Education 8 Delivery of health care 7 Health Services Research 7 Health Surveys 7 Child 5 Developing countries 5 Drug and narcotic control 5 Food and Agriculture Organization of the United Nations 5 Institutional Management Teams 5 Managed Care Programs 5 Research 5 Staff Development 5 Analgesics, opioid 4 Cost of illness 4 Pain classification 4 Pain drug therapy 4 Pain measurement 4 Palliative care 4 Public Health 4 Public health 4 Reference standards 4 adverse effects 4 Biological products standards 3 Chronic disease prevention and control 3 Communicable disease control 3 Drugs, essential 3