Yosio MUTO "On conformally curved Riemann spaces $V_{n},$ $n\geqq 6$ , admitting a group of motions $G_{r}$ of order $r>n(n+1)/2-(3n-11)$ .," Journal of the Mathematical Society of Japan, J. Math. Soc. Japan 9(1), 38-61, (January, 1957)