1. Informetrics Research Group, Ton Duc Thang University, Ho Chi Minh City, Vietnam
2. Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam
3. The School of Mining Engineering, University of the Witwatersrand, Johannesburg, South Africa
4. Mining and Mineral Processing Engineering Department, Taita Taveta University, Voi, Kenya
5. School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, Johannesburg, South Africa