1. Bhavanandan V. P., Studies on the use of urea as a fertilizer for tea in Ceylon. I — Introduction and preliminary observations. Tea Quarterly 41, 87–93 (1970).
2. Bhavanandan V. P. and Fernando V., Studies on the use of urea as a fertilizer for tea in Ceylon. II — Urease activity in tea soils. Tea Quarterly 41, 94–106 (1970).
3. Bremner J. M. and Douglas L. A., Inhibition of urease activity in soils. Soil Biol. Biochem 3, 297–307 (1971).
4. Crowther A. B. and Large R. S., Improved conditions for sodium phenoxide, sodium hypochlorite method for determination of ammonia. Analyst 81, 64–65 (1956).
5. Dagley S., The microbial metabolism of phenolics, p. 287 in Soil Biochemistry Ed. A. D. McLaren and G. H. Peterson. Edward Arnold. Lond. 1967.