1. Asthma, wheezing, and school absence in primary schools;Hill, R.A.; Standen, P.J.; Tattersfield, A.E.;Arch Dis Child,1989
2. Measuring disease specific quality of life in clinical trials;Guyatt, G.H.; Bombardier, C.; Tugwell, P.X.;Can Med Assoc J,1986
3. Measuring health status;Hunt, S.M.; McEwen, J.; McKenna, S.P.,1986
4. Armitage P, Berry G. Statistical methods in medical research. 2nd Ed. Oxford: Blackwell, 1987.
5. Attitude measurement: use of co-efficient alpha with cluster or factor analysis;McKenneli, A.;Sociology,1970