Istre GR, Conner JS, Broome CV, et al. «Risk factors for primary
invasive Haemophilus influenzae disease: increased risk from day care attendance and school - aged household members.»
Cochi SL, Fleming DW, Hightower AW, et al. «Primary
invasive Haemophilus influenzae type b disease: a population - based assessment of risk factors.»