Buser finite length spectrum theorem ($L=L(g,\epsilon )$)

For fixed genus $g\ge 2$ and systole lower bound $\epsilon >0$, a uniform finite length cutoff $L$ determines the entire unmarked length spectrum of a closed hyperbolic surface in the thick part, including multiplicities. Equality up to $L$ forces equality everywhere. This is a finite-determination statement for spectra and does not claim that all isospectral surfaces are isometric.