-------             -------
             | 0 | 0 |           |   | 1 |
        13.  |---|---|      14.  |---|---|
             |   | 0 |           | 1 |   |
              -------             -------
              -------             -------
             | 1 |   |           | 0 | 1 |
        15.  |---|---|      16.  |---|---|
             |   | 0 |           | 1 | 0 |
              -------             -------

![See pp. 65, 6]

1. Larger Diagram.

Propositions to be represented.

                     -----------
                    |     |     |
                    |   --x--   |
                    |  |  |  |  |