+.Ss \&Xc
+Close a scope opened by
+.Sx \&Xo .
+.Ss \&Xo
+Open an extension scope. This macro originally existed to extend the
+9-argument limit of troff; since this limit has been lifted, the macro
+has been deprecated.
+.Ss \&Xr
+Link to another manual
+.Pq Qq cross-reference .
+Its calling syntax is
+.Pp
+.D1 \. Ns Sx \&Xr Cm name section
+.Pp
+The
+.Cm name
+and
+.Cm section
+are the name and section of the linked manual. If
+.Cm section
+is followed by non-punctuation, an
+.Sx \&Ns
+is inserted into the token stream. This behaviour is for compatibility
+with