1. Chemical Resource Beneficiation, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
2. C.D. Nenitescu Center of Organic Chemistry of the Romania Academy, Splaiul Independentei, 202B, Bucharest, Romania
3. Department of Chemistry, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031, South Africa