RT Journal Article SR Electronic T1 Family size, infection and atopy: the first decade of the 'hygiene hypothesis' JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP S2 OP 10 DO 10.1136/thorax.55.suppl_1.S2 VO 55 IS suppl 1 A1 DP Strachan YR 2000 UL http://thorax.bmj.com/content/55/suppl_1/S2.abstract AB