1. Anderson R. M. & May R. M. 1976 The invasion persistence and spread of infectious diseases within animal
2. of h arb o u r seals ( Phocavitulina) in some waters around
3. and plant communities. Phil. Trans. R. Lond. B 314
4. Europe in 1988-1989 (H arw ood 1990). Mass deaths of
5. seals with sim ilar symptoms in the N orth A tlantic have