References
- Hogg , R. V. and Craig , A. T. 1970 . Introduction to Mathematical Statistics, , 3rd ed. , 307 Macmillan Company .
- Mood , A. M. , Graybill , F. A. and Boes , D. C. 1974 . Introduction to the Theory of Statistics, , 3rd ed. , 419 McGraw-Hill . 474