contract ERC20Token is ERC20Interface, Owned {
  
  using SafeMath3 for uint;

  uint public tokensIssuedTotal = 0;
  mapping(address => uint) balances;
  mapping(address => mapping (address => uint)) allowed;

  // Functions ------------------------

  /* Total token supply */

  function totalSupply() constant returns (uint) {
    return tokensIssuedTotal;
  }

  /* Get the account balance for an address */

  function balanceOf(address _owner) constant returns (uint balance) {
    return balances[_owner];
  }

  /* Transfer the balance from owner's account to another account */

  function transfer(address _to, uint _amount) returns (bool success) {
    // amount sent cannot exceed balance
    require( balances[msg.sender] >= _amount );

    // update balances
    balances[msg.sender] = balances[msg.sender].sub(_amount);
    balances[_to]        = balances[_to].add(_amount);

    // log event
    Transfer(msg.sender, _to, _amount);
    return true;
  }

  /* Allow _spender to withdraw from your account up to _amount */

  function approve(address _spender, uint _amount) returns (bool success) {
    // approval amount cannot exceed the balance
    require ( balances[msg.sender] >= _amount );
      
    // update allowed amount
    allowed[msg.sender][_spender] = _amount;
    
    // log event
    Approval(msg.sender, _spender, _amount);
    return true;
  }

  /* Spender of tokens transfers tokens from the owner's balance */
  /* Must be pre-approved by owner */

  function transferFrom(address _from, address _to, uint _amount) returns (bool success) {
    // balance checks
    require( balances[_from] >= _amount );
    require( allowed[_from][msg.sender] >= _amount );

    // update balances and allowed amount
    balances[_from]            = balances[_from].sub(_amount);
    allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_amount);
    balances[_to]              = balances[_to].add(_amount);

    // log event
    Transfer(_from, _to, _amount);
    return true;
  }

  /* Returns the amount of tokens approved by the owner */
  /* that can be transferred by spender */

  function allowance(address _owner, address _spender) constant returns (uint remaining) {
    return allowed[_owner][_spender];
  }

}
// ----------------------------------------------------------------------------
//
// ERC Token Standard #20
//
// ----------------------------------------------------------------------------
function approve(address _spender, uint _amount) returns (bool success) {
  // approval amount cannot exceed the balance
  require ( balances[msg.sender] >= _amount );
      
  // update allowed amount
  allowed[msg.sender][_spender] = _amount;
    
  // log event
  Approval(msg.sender, _spender, _amount);
  return true;
}

/* Allow _spender to withdraw from your account up to _amount */