1. School of Mathematics and Statistics; The University of Sydney; NSW 2006 Australia
2. Department of Mathematics and Actuarial Science; Indiana University Northwest; 3400 Broadway Gary IN 46408 USA
3. Faculty of Architecture, Computing and Humanities; Department of Mathematical Sciences; University of Greenwich; London SE10 9LS United Kingdom
4. Honorary Associate at the School of Mathematics and Statistics; The University of Sydney; NSW 2006 Australia