Ichiro Yokota "3-graded decompositions of exceptional Lie algebras $\mathfrak{g} $ and group realizations of $\mathfrak{g}_{ev}, \mathfrak{g}_0$ and $\mathfrak{g}_{ed}$ Part I, $G = G_2,F_4,E_6$," Journal of Mathematics of Kyoto University, J. Math. Kyoto Univ. 41(3), 449-474, (2001)