1. American Conference of Governmental Industrial Hygienist. 1983.Threshold Limit Values for Chemical Substances and Physical Agents in the Word Environment, 10–43. Cincinnati, Ohio: ACGIH. first printing
2. Reduced prevalence and growth rate of urethane induced lung adenomas in ageing adult strain a mice
3. Freund, J. E., Livermore, P. E. and Miller, I. 1960.Manual of Experimental Statistics, 74Engle‐wood Cliffs, N.J.: Prentice‐Hall.