訂正日: 2006/08/29訂正理由: -訂正箇所: 引用文献情報訂正内容: Right : (1) J. Eiesland, Trans. Amer. Math. Soc., 27, (1925), 213. (2) This theorem was read at the annual meating of the Math. Soc. of Japan held in Nov. 1, 1948. We can prove this by showing that ρ1=0 is equivalent to the vanishing of the conformal curvature tensor. (3) H. Takeno, Jour. Sci. Hiroshima Univ. 11, (1942), 228. (4), (5) H. Takeno, Jour. Sci. Hiroshima Univ. 12, (1942), 131.