1. Chambers, E. G. (1958). Statistical calculation for beginners (p. 61). The University Press.
2. Chemical bonding
3. Cochran, W. G. & Cox, G. M. (1963). Experimental design (p. 347). Asia Publishing House.
4. Das, N. G. (1990). Statistical methods in commerce, accountancy & economics, Part I. M (p. 318 & 333). Das and Co.