1. Abbas, A. K. Cell 84, 655–657 (1996).
2. Wang, J. et al. Cell 98, 47–58 (1999).
3. Thornberry, N. A. & Lazebnik, Y. Science 281, 1312–1316 (1998).
4. Thompson, C. B. Science 267, 1456–1462 (1995).
5. Canale, V. & Smith, C. J. Pediatr. 70, 891–899 (1967).