Some Coble surfaces admit only Bertini involutions

Source abstract

In this article we show that a biregular involution $i : X \to X$ defined on an unnodal Coble surface $X$ with irreducible boundary curve $\{C\} = |- 2 K_X|$ is necessarily a lift of a Bertini involution. Then we show with counterexamples that the hypothesis of irreducibility of $C$ and unnodality of $X$ are both necessary.