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[^1]: With Statistical Help from C. Chandrashekhar, M.SC.,  Ph.D., M.P.H., *Population Division, U.N.O.; Formerly Professor of Statistics, All-India Institute of Hygiene and Public Health*

[^2]: A summary of the paper was read at the 35th session of the Indian Science Congress at Patna in 1948. 

    The work was carried out at Shillong in 1941, and at Kalimpong and Gangtok in 1942.