function set_tokens_received() {
    require(msg.sender == owner);
    uint256 previous_balance;
    uint256 tokens_this_round;
    for (uint8 i = 0; i < snapshots.length; i++) {
      previous_balance += snapshots[i].tokens_balance;
    }
    tokens_this_round = token.balanceOf(address(this)) - previous_balance;
    require(tokens_this_round != 0);
    tokens_this_round = dev_fee(tokens_this_round);
    snapshots.push(Snapshot(tokens_this_round, eth_balance));
    rounds++;
  }