ag-gipp/GoUldI

4(\boldsymbol{{\eta}}^{1}(T_{1})\cdot\boldsymbol{{\eta}}^{2}(T_{2})-\boldsymbol{{\eta}}^{2}(T_{1})\cdot\boldsymbol{{\eta}}^{1}(T_{2}))=|T_{1}\cap T_{2}|\pmod{2}