Constraints on spin observables in antiproton-proton to antiLambda-Lambda

It is recalled that spin-observables in the strangeness-exchange reaction $\bar{p}{p} \to \bar{\Lambda}{\Lambda}$ are not independent but are related to each other by simple algebraic relations. This provides constraints on the existing data on polarization and spin-correlation coefficients, and also on the forthcoming data obtained using a polarized proton target.