TY  - BOOK
AU  -  World Health Organization 
TI  - Sample size determination in health studies: a practical manual
SN  - 92 4 154405 8
U1  - WA950 
PY  - 1991///
CY  - Geneva
PB  - W H O
KW  - Sampling Studies
KW  - Health Surveys
N2  -  Health Surveys, Sampling Studies
ER  -