-Finally, I will discuss a variant of our "running example" intrusive collection that this model can *not* handle, and how the model could be extended.
-This extended model will actually call for a change to the `Pin` API (or rather, for a revert to an earlier version).
+Finally, I will discuss a variant of our "running example" intrusive collection that combines shared references and pinning.
+It turns out this variant is actually incompatible with the formal model from the last post, but the model can be extended to fix this.
+Hiwever, this extended model will actually call for a change to the `Pin` API (or rather, for a revert to an earlier version).