1. See the review on the $$K_{t_3 } $$ decay byM. K. Gaillard andL. M. Chounet: CERN Report No. 70-14 (1971).
2. For recent data, see the report byS. Wojcicki:Proceedings of the XVI International Congress on High-Energy Physics, Batavia, 1972 (to be published).
3. Study of the $$K_{t_3 } $$ decay by the soft-pion treatment was first made byC. G. Callan andS. Treiman:Phys. Rev. Lett.,16, 153 (1966).
4. See,e.g.,S. Matsuda andS. Oneda:Phys. Rev.,169, 1172 (1968). Also,S. Oneda andH. Yabuki:Phys. Rev. D,3, 2743 (1971).
5. The «hard meson» technique has been used by many authors; seeR. Arnowitt: Rapporteur talk,Proceedings of the Conference on ππ and Kπ Interactions (Argonne, Ill. 1969).