1. Abdullaeva A A and Dokl A N 1959 Vz S.S.R. 1, 43–45.
2. Arnold C G 1958 Z. Bot. 46 516–549.
3. Arora D K and Dwivedi R S 1979 Sacc. Soil Biol. and Biochem. 11, 563–566.
4. Chandra H 1984 Ph.D. Thesis, University of Gorakhpur, India.
5. Chaturvedi R 1979 Ph.D. Thesis, University of Gorakhpur, India.