訂正日: 2006/09/26訂正理由: -訂正箇所: 引用文献情報訂正内容: Right : [1] J. W. Gray, Some global properties of contact structure, Ann. of Math., 69 (1959), 421-450. [2] S. Sasaki, On differentiable manifolds with certain structures which are closely related to almost contact structure I, Tôhoku Math. J., 12 (1960), 456-476. [3] S. Sasaki and Y. Hatakeyama, On differentiable manifolds with certain structures which are closely related to almost contact structure II, Tôhoku Math. J., 13 (1961), 281-294. [4] S. Sasaki and C. J. Hsu, On the integrability of almost contact structures, to appear Tôhoku Math. J., 14 (1962).