1. Anjana SU, Iqbal M, Abrol YP (2007) Are nitrate concentrations in leafy vegetables within safe limits? Curr Sci 92(3):356–360
2. Asdal Å, Breland TA (2003) Compost quality related to product utilization in Norway. In: Pullammanappallil PMA, Diaz LF, Bidlingmaier W (eds) Proceedings of the fourth international conference of ORBIT association on biological processing of organics: advances for a sustainable society, Perth, Australia. Organic Recovery & Biological Treatment. Organic Recovery & Biological Treatment, pp 230–240
3. FAO Fisheries and Aquaculture Technical Paper;K Barrington,2009
4. Berry PM, Sylvester-Bradley R, Philipps L et al (2002) Is the productivity of organic farms restricted by the supply of available nitrogen? Soil Use Manag 18:248–255. doi: 10.1079/sum2002129
5. Breland TA (1996a) Green manuring with clover and ryegrass catch crops undersown in small grains: crop development and yields. Acta Agric Scand Sect B Soil Plant Sci 46:30–40