Ekere, N.R., et al. “Distribution and Health Risks of Nitrate and Heavy Metals in Edible Leafy Vegetables Grown in Sewage Sludge and Wastewater-Amended Agricultural Soils”. Asian Journal of Chemistry, vol. 28, no. 1, Oct. 2015, pp. 6-10, doi:10.14233/ajchem.2016.19117.