Takashi Sakai "The contact structures on $\{{\rm SU}(n+1)\times R/{\rm SU}(n)\times \ R\}_{\alpha}$ and $\{{\rm Sp}(n)\times {\rm SU}(2)/{\rm Sp}(n-1)\times \ {\rm SU}(2)\}_{\alpha}$ of Berger," Tohoku Mathematical Journal, Tohoku Math. J. (2) 25(2), 145-155, (1973)