Cochran W.G, . (1990). Sampling Techniqes. New Delhi: Wiley Easten LTD.
Cochran W.G, . 1990. Sampling Techniqes. New Delhi: Wiley Easten LTD.
Cochran W.G, . Sampling Techniqes. New Delhi: Wiley Easten LTD. 1990.
