Change as suggested by Peter Funk <pf@artcom-gmbh.de>:

Create a hyperlink between the language reference and documentation for
the built in functions.

Doc/ref/ref5.tex

@@ -453,8 +453,9 @@ function call.
 \obindex{function}
 
 \item[a built-in function or method:] The result is up to the
-interpreter; see the library reference manual for the descriptions of
-built-in functions and methods.
+interpreter; see the \citetitle[../lib/built-in-funcs.html]{Python
+Library Reference} for the descriptions of built-in functions and
+methods.
 \indexii{function}{call}
 \indexii{built-in function}{call}
 \indexii{method}{call}