Equation 23.2.309A2166571118

\begin{equation} \begin{split} \tau \omega & =\eta +\lambda \wedge \lambda ^{\mathrm c},\\ \eta (U,JV)& =\frac1{4\pi }\bigl (sg(U,V)-\lambda (U)\lambda (V)-\lambda (JU)\lambda (JV)\bigr ). \end{split} \end{equation}