1. Recent review is contained in: A.Yu. Smirnov: ICTP preprint IC/93/388
2. K. Lande et al.: in Proc: XXVth Int. Conf. on High Energy Physics, Singapore, K.K. Phua, Y. Yamaguchi, (eds.) World Scientific (Singapore: 1991); K.S. Hirata et al.: Phys. Rev. Lett. 66(1991) 9; P. Anselman et al.: Phys. Lett. B285 (1992) 376; A. I. Abazov et al.: Phys. Rev. Lett. 67 (1991) 3332; V. Gavrin, talk at the Int. Conf. on High Energy Physics. Dallas, 1992
3. V. Barger et al.: Phys. Rev. D43 (1991) 1110: A. Acker, S. Pakvasa, J. Pantaleone, Phys. Rev. D43 (1991) 1754; P.I. Krastev, S.T. Petcov: Phys. Lett. B299 (1993) 99
4. S.P. Mikheyev, A.Yu. Smirnov: Yad. Fiz. 42 (1985) 1414; L. Wolfenstein: Phys. Rev. D17 (1978) 2369; For a review on the msw effect, see, P.B. Pal. Oregon Univ. Preprint, OITS 470 (1991)
5. K.S. Hirata et al.: Phys. Lett. B280 (1992) 146