[EM] Practical democracy as a serialized cascade tree

[Michael Allan]

Sorry, the first diagram has typos in X Y Z.  It should be:

   Practical:
   ---------
 1
   (A) (B) (C) (D) (E) (F) (G) (H) (I) (J) (K) (L) (M) (N) (O) (P) (Q) (R)
    |  /    |  /    |  /    |  /    |  /    |  /    |  /    |  /    |  /
    | /     | /     | /     | /     | /     | /     | /     | /     | /
    |/      |/      |/      |/      |/      |/      |/      |/      |/
   (S)     (T)     (Y)     (U)     (V)     (Z)     (W)     (X)     (AA)

 2
   (S)     (T)             (U)     (V)             (W)     (X)
    |      /                |      /                |      /
    |  ---                  |  ---                  |  ---
    |/                      |/                      |/
   (Y)                     (Z)                     (AA)

 3
   (Y)                     (Z)
    |                      /
    |  -------------------
    |/
   (AA)