Graham Ellis 
Mathematics Department 
National University of Ireland, Galway 
e-mail: graham.ellis (at) nuigalway.ie
    Web: 
    http://hamilton.nuigalway.ie  
 Graham Ellis 
Mathematics Department 
National University of Ireland, Galway 
e-mail: graham.ellis (at) nuigalway.ie
    Web: 
    http://hamilton.nuigalway.ie