1. Ahrens LH (1979) Origin and distribution of the elements. Pergamon, New York London
2. Aleem MIH (1970) Oxidation of inorganic nitrogen compounds. Annu Rev Plant Physiol 21: 67–90
3. Aleem MIH (1977) Energy coupling in chemolithotrophic bacteria. Symp Soc Gen Microbiol 27: 351–381
4. Alexander M (1965) Nitrification. In: Bartholomew WV, Clark FE (eds) Soil nitrogen. Am Soc Agron, Madison
5. Alexander MK, Marshall KC, Hirsch P (1960) Auto trophy and hetero trophy in nitrification. Trans 7th Int Congr Soil Sci, Madison 2: 586–591