[1] National Centre for Hospital Hygiene,
[2] Statens Serum Institut,undefined
[3] Artillerivej 5,undefined
[4] DK-2300 Copenhagen S,undefined
[5] Denmark,undefined
[6] Biostatistical Department,undefined
[7] Statens Serum Institut,undefined
[8] Artillerivej 5,undefined
[9] DK-2300 Copenhagen S,undefined
[10] Denmark,undefined