function migrate(uint256 amount) {

    
    if (!isFinalized) 
      revert();

    
    if (migrateDisabled) 
      revert();

    
    if (pendingMigrations[msg.sender].amount > 0)
      revert();


    
    StandardToken(previousToken).transferFrom(msg.sender, this, amount);

    
    pendingMigrations[msg.sender].dateTimeCreated = now;
    pendingMigrations[msg.sender].amount = amount;
  }