In exercise [1, p. 34 exercise 2.8] we are asked to find the inverse of the $n\times n$ hermitian matrix $\mathbf{R}$ given by [1, (2.27)] by recursively applying Woodbury’s identity. This should be done by considering the cases where $f_{1},f_{2}$ are arbitrary and where $f_{1}=k/n$, $f_{2}=l/n$ for $k,l$ beeing distinct integers in the range $\left[ -n/2,n/2-1 \right]$ for $n$ even and $\left[ -(n-1)/2,(n-1)/2 \right]$ for $n$ odd. read the conclusion >