A. Mbangi, P. Muchaonyerwa, and R. Zengeni, “Accumulation of multiple heavy metals in plants grown on soil treated with sewage sludge for more than 50 years presents health risks and an opportunity for phyto-remediation”, WSA, vol. 44, no. 4 October, Oct. 2018, doi: 10.4314/wsa.v44i4.06.