1. Methods for the study of nitrogenase activity in field grown grasses;Abrantes;Soil Biology International News Bulletin Lyon,1975
2. Limiting factors in grass nitrogen fixation;Balandreau,1978
3. Evaluation of acetylene reduction by excised roots for the determination of nitrogen fixation in grasses;van Berkum;Soil Biology & Biochemistry,1980
4. Statistics and Biologists;Campbell,1974
5. Practical Non-parametric Statistics;Conover,1971