Pointer Validity
----------------
Note that all pointers to objects that have an Id have only a limited
-validity period, with the exception of Repo pointers. There are only
+validity period, with the exception of Repo pointers. They are only
guaranteed to be valid until a new object of that type is added or an
object of that type is removed. Thus pointers to Solvable objects are only
valid until another solvable is created, because adding a Solvable may