Remarks about spin measurements in $\bar{\rm p}{\rm p} \to \overline{\Lambda}{\Lambda}$

We comment on the proposed measurement of the spin-depolarisation parameter $D_{nn}$ in the strangeness-exchange reaction $\bar{\rm p}{\rm p} \rightarrow \overline{\Lambda}{\Lambda}$. It is shown that the existing data on the correlation coefficients $C_{ij}$ limit the range allowed for $D_{nn}$.