1. A.D. Johnson (Senior Lecturer), University of Huddersfield, Huddersfield U.K., 2013.
2. Open source.
3. D. Warburton (Research Student), University of Huddersfield, Huddersfield U.K., 2012.
4. R. Taylor (Senior Lecturer), University of Huddersfield, Huddersfield U.K., 2012.
5. Scribd.com, www.scribd.com/doc/50459583/Example-Product-Design-Specification, 2012.