Visual cryptography (VC), first proposed by Naor and Shamir, is a variant of secret sharing with many applications, such as providing secure services in communications. In 2006, Horng et al. showed that VC is vulnerable to cheating attacks. They also presented two approaches to prevent cheating, namely share authentication and blind authentication. In this paper, we review some share authentication based cheating prevention schemes and propose a new one for Noar-Shamir's (2, n)-VC.