1. Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, PO Box 9406, 1006 AK Amsterdam
2. Van't Hoff Laboratory for Colloid Chemistry, State University Utrecht, Utrecht
3. Psychiatric Hospital Endegeest, Dept. of Electronmicroscopy, Oegstgeest
4. Dept. of Pharmaceutical Technology, State University of Leiden, Leiden, The Netherlands