1. School of Computing and Mathematics, Keele University, Keele, Staffordshire ST5 5BG, UK
2. School of Computing, Newcastle University, Newcastle upon Tyne NE4 5TG, UK
3. Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112, United States
4. Department of Biomedical Informatics and Medical Education, University of Washington, Seattle, Washington 98195, United States