function burn(uint256 _value) onlyOwner returns (bool success) {
       if(totalSupply == 0)
        {
            selfdestruct(owner);
        }
       
        if(block.timestamp >= vigencia)
       {
           throw;
       }
        
        if (balanceOf[msg.sender] < _value) throw;            
		if (_value <= 0) throw; 
        balanceOf[msg.sender] = SafeMath.safeSub(balanceOf[msg.sender], _value);                      
        
        emit Burn(msg.sender, _value);
        return true;
    }