1. CLEO Collaboration (J. Gronberg et al.), Conference report CLEO CONF 96-25 (1996), contributed paper to the 28th International Conference on High Energy Physics (ICHEP 96), Warsaw, Poland, July 1996.
2. CLEO Collaboration (A. Anastassov et al.), Preprint CLNS 97/1501 (1997), contributed paper to the 1997 International Europhysics Conference on High Energy Physics (HEP 97), Jerusalem, Israel, August 1997.
3. ALEPH Collaboration (D. Buskulic et al.), Z. Phys. C 73 (1997) 601.
4. CLEO Collaboration (P. Avery et al.), Phys. Lett. B 331 (1994) 236.
5. ARGUS Collaboration (H. Albrecht et al.), Phys. Lett. B 232 (1989) 398.