@@ -143,7 +143,7 @@ which is its address. The root of the tree is `1`; if the
143143address of a cell is `n`, its head is `2n` and its tail is
144144`2n+1`.
145145
146−A picture might help::
146+A picture might help:
147147```
148148 1
149149 / \
@@ -152,7 +152,7 @@ A picture might help::
152152 4 5 6 7
153153 / \
154154 14 15
155−```
155+```
156156
157157The syntax for a fragment of the subject at a tree address, or
158158*axis*, is just `+axis`. So:
@@ -219,7 +219,7 @@ table here -- just a tree search.
219219
220220An expression like the label `x` or the axis `+2`, which
221221designates a fragment or feature of the subject, is called a
222−*limb*. A list of limbs connected with `.`, is a *wing*.
222+*limb*. A list of limbs connected with `.` is a *wing*.
223223
224224To remind you that you're not in Kansas anymore, the syntax for a
225225wing, like `q.y` above, means means "q inside y." In a classic