1. Robbins, J.B. et al. J. Infect. Dis. 191, 81–88 (2005).
2. Rappuoli, R., Miller, H.I. & Falkow, S. Science 297, 937–939 (2002).
3. Ellis, R.E. in New Generation Vaccines (eds. Woodrow, G.C. & Levine, M.M.) 439–447 (Marcel Dekker, New York and Basel, Switzerland, 1990).
4. Wenger, J., Campbell, H., Miller, E. & Salisbury, D. in New Generation Vaccines 3rd edn. (eds. Levine, M.M., Kaper, J.B., Rappuoli, R., Liu, M.A. & Good, M.F.) 427–441 (Marcel Dekker, New York and Basel, Switzerland, 2004).
5. Pizza, M. et al. Science 246, 497–500 (1989).