1. A. Butterworth, Clinical Veterinary Science, Univ. of Bristol, Langford, N. Somerset, UK.
2. K. M. E. Turner, School of Social and Community Medicine, Univ. of Bristol, Bristol, UK.
3. N. Jennings ()(), Dotmoth, 1 Mendip Villas, Crabtree Lane, Dundry, Bristol, BS41 8LN, UK