function areAllTokensAllowed(address[] _tokens) external view returns (bool)
    {
        for (uint i = 0; i < _tokens.length; i++)
        {
            if (address(priceOracle[_tokens[i]]) == address(0x0) &&
                address(kyberOracle[_tokens[i]]) == address(0x0))
            {
                return false;
            }
        }
        return true;
    }