    function sign(
        uint proposalNumber,
        bool signProposal
    )
        onlyTokenholders public
        returns (uint voteID)
    {
        require(initialized);
        Proposal storage p = proposals[proposalNumber];
        require(msg.sender == chairmanAddress);
        require(signProposal == true);
        p.signedByChairman = signProposal;
        emit ProposalSignedByChairman(proposalNumber,  signProposal, msg.sender);
        return proposalNumber;
    }