1. Abrahams, E.W., Harland, R.D.: Sensitivity to avian and human PPD in Brisbane school children. Tubercle (Lond.)16, 79–94 (1967)
2. Allison, A.C., Harrington, J.S., Berbeck, M.: An examination of the cytoxic effects of silica on makrophages. J.exp.Med.124, 141 (1966)
3. Ast, D.: Tuberkulintestungen bei der Bundeswehr, Prax.Pneumol.26, 338–345 (1972)
4. Blum, H.L., Hesse, F.E., Kent, G.W., Lichtenstiger, D.S.: A tuberculin-testing survey of a school age population in eleven areas in California. Amer.Rev.resp.Dis.87, 181–199 (1963)
5. Christensen, O.: Epidemiological problems in tuberculosis. Scand.J.resp.Dis., Suppl.65, 25–34 (1968)