1. The WHO Collaborating Centre for Research in Human Reproduction, Santiago, Chile
2. The Dept. of Obstetrics and Gynaecology, Trinity College Medical School, St. James'and Rotunda Hospitals, University of Dublin, Dublin, Ireland
3. The WHO Collaborating Centre for Research in Human Reproduction, Salvador, Brazil
4. The WHO Collaborating Centre for Research in Human Reproduction, Singapore
5. The UK Reference Laboratory for Anticoagulant Reagents and Control, Withington Hospital, University Hospital of South Manchester, Manchester, United Kingdom
6. The Special Programme of Research, Development and Research Training in Human Reproduction, World Health Organization, Geneva, Switzerland