References
- Cochran , W. G. 1963 . Sampling Techniques, Second Edition , New York : John Wiley and Sons, Inc. .
- Hansen , M. H. 1953 . Sample Survey Methods and Theory, Volume 2 , New York : John Wiley and Sons .
- Olkin , I. 1958 . “Multivariate ratio estimation for finite populations,” . Biometrika , 45 : 154 – 65 .