In 2005, Wang, et al. proposed a threshold proxy multi designated-verifiers signature scheme (Wang-Fu) by combining the properties of the threshold proxy signature and the multi designated-verifiers signature. In the same year, Chen, et al. also proposed a designated-verifier signature scheme. It is shown that the manager of the set of all verifiers can directly forge signatures, so that, each verifier should give zero knowledge proof for the partial data generated in verifying phase by using his secret key, and that CFT (Chen-Feng-Tan) scheme does not satisfy the non-transferability, i.e., the designated-verifier can prove to a third party that the signature is generated by the signer. The reason is that the scheme directly follows from the technique in Schnorr signature. The designated-verifier can easily transform the signature into a common signature with respect to the signer's public parameters.