I am reading a paper about digital filtering (for the very first time) and I found this notation (double arrow with $z$ above) which I do not quite understand.
Could you please give me some hint?
Defining the inverse convolution operator $(b_1^n)^{-1}(k) \stackrel{z}{\longleftrightarrow} 1 / B_1^n(z)$, the solution is found by inverse filtering (cf. [97])
It is a Z transform. Just like Fourier transform, it turns convolutions into multiplications, so it can be used to undo convolutions.