Abstract
References
1.
Gurney
C
Roth
M
Garside
R F
. (1970 ) Proc. roy. Soc. Med.
63 , 232 .
2.
McNemar
Q
. (1962 ) Psychological Statistics . 3rd ed . New York .
3.
Maxwell
A E
. (1961 ) Analysing Qualitative Data . London .