1. School of Mathematics and Statistics; University of St Andrews; St Andrews U.K.
2. Medical Research Council Biostatistics Unit; Cambridge U.K.
3. Department of Mathematics and Statistics; University of Strathclyde; Glasgow U.K.
4. School of Health and Life Sciences; Glasgow Caledonian University; Glasgow U.K.
5. Health Protection Scotland; Glasgow U.K.
6. Centre for Public Health; Liverpool John Moores University; Liverpool U.K.