Index: Doc/library/functions.rst
===================================================================
--- Doc/library/functions.rst	(Revision 83182)
+++ Doc/library/functions.rst	(Arbeitskopie)
@@ -1082,10 +1082,21 @@
 .. function:: sum(iterable[, start])
 
    Sums *start* and the items of an *iterable* from left to right and returns the
-   total.  *start* defaults to ``0``. The *iterable*'s items are normally numbers,
-   and are not allowed to be strings.  The fast, correct way to concatenate a
-   sequence of strings is by calling ``''.join(sequence)``.  To add floating
-   point values with extended precision, see :func:`math.fsum`\.
+   total. *start* defaults to ``0``. The *iterable*'s items are normally numbers.
+   The *start* value must not be a string.
+   
+   .. note::
+      Using sum to concatenate sequences will result 
+      in quadratic run-time performance.
+   
+   Alternatives:
+      - To concatenate strings, use 
+        ``''.join(str_iterable)`` (see :func:`str.join`).  
+      - To concatenate lists, use 
+        :func:`itertools.chain.from_iterable() 
+        <itertools.itertools.chain.from_iterable>`.
+      - To add floating point values with extended precision, 
+        use :func:`math.fsum`.
 
 
 .. function:: super([type[, object-or-type]])