- Author: Margriet Sitskoorn
- Language: English
- Year: 2019
- Author: Johann Broodryk
- Language: English
- Year: 2005
- Author: Johnson Spencer, D M
- Language: Portuguese
- Year: 1998
- Author: Stewart Matthew
- Language: English
- Year: 2009
- Author: Stewart Matthew
- Language: English
- Year: 2009
- Author: Bharat S. Thakkar
- Language: English
- Year: 2020
- Author: Matthew Stewart
- Language: English
- Year: 2009
- Author: Gunter Dueck
- Language: German
- Year: 2004