-For $D=R$,
-xxx up to here?
-
-If $L \in \py, R \in \py$: not applicable for either $D=L$ or $D=R$.
-
-If $L \in \py, R \in \pn$: not applicable for $L$, OK for $R$.
-
-Other possibilities for $L \in \py$ are excluded by Tip Merge.
-
-If $L \in \pn, R \in \pn$: satisfied for both $L$ and $R$.
-
-If $L \in \pn, R \in \foreign$: satisfied for $L$, not applicable for
-$R$.
-
-If $L \in \pn, R \in \pqy$: satisfied for $L$, not applicable for
-$R$.
-
-Other possibilities for $L \in \pn$ are excluded by Base Merge.
-
-If $L \in \foreign$: not applicable for $L$; nor for $R$, by Foreign Merges.
+For $D = R \in \set R, R \in \pn$: $D \in \pn, \pd = \p, C \in \pn$ as
+for $D = L$.