1. Percival, A., Armstrong, E.C., Turner, G.C. (1969) Increase of incidence of Tetracycline resistant pneumococci in Liverpool in 1968. Lancet, 1, 998–1000.
2. Robertson, M. H. (1965) 0-haemolytic streptococci in South West Essex with reference to tetracycline resistance. B. M. J., 2, 569-571.
3. Robertson, M.H. (1968) Tetracycline resistant streptococci in South West Essex: a continuing survey. B.M.J., 3, 349–350.
4. Robertson, M. H. (1973) Tetracycline resistant ß-haemolytic streptococci in South West Essex: decline and fall. B. M. J., 4, 84–85.