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diff --git a/src/Text/Pandoc/Slides.hs b/src/Text/Pandoc/Slides.hs
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+{-
+Copyright (C) 2012-2016 John MacFarlane <jgm@berkeley.edu>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+-}
+
+{- |
+   Module      : Text.Pandoc.Slides
+   Copyright   : Copyright (C) 2012-2016 John MacFarlane
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : John MacFarlane <jgm@berkeley.edu>
+   Stability   : alpha
+   Portability : portable
+
+Utility functions for splitting documents into slides for slide
+show formats (dzslides, revealjs, s5, slidy, slideous, beamer).
+-}
+module Text.Pandoc.Slides ( getSlideLevel, prepSlides ) where
+import Text.Pandoc.Definition
+
+-- | Find level of header that starts slides (defined as the least header
+-- level that occurs before a non-header/non-hrule in the blocks).
+getSlideLevel :: [Block] -> Int
+getSlideLevel = go 6
+  where go least (Header n _ _ : x : xs)
+                 | n < least && nonHOrHR x = go n xs
+                 | otherwise               = go least (x:xs)
+        go least (_ : xs) = go least xs
+        go least [] = least
+        nonHOrHR (Header{}) = False
+        nonHOrHR (HorizontalRule) = False
+        nonHOrHR _ = True
+
+-- | Prepare a block list to be passed to hierarchicalize.
+prepSlides :: Int -> [Block] -> [Block]
+prepSlides slideLevel = ensureStartWithH . splitHrule . extractRefsHeader
+  where splitHrule (HorizontalRule : Header n attr xs : ys)
+                       | n == slideLevel = Header slideLevel attr xs : splitHrule ys
+        splitHrule (HorizontalRule : xs) = Header slideLevel nullAttr [Str "\0"] :
+                                           splitHrule xs
+        splitHrule (x : xs)              = x : splitHrule xs
+        splitHrule []                    = []
+        extractRefsHeader bs             =
+          case reverse bs of
+               (Div ("",["references"],[]) (Header n attrs xs : ys) : zs)
+                 -> reverse zs ++ (Header n attrs xs : [Div ("",["references"],[]) ys])
+               _ -> bs
+        ensureStartWithH bs@(Header n _ _:_)
+                       | n <= slideLevel = bs
+        ensureStartWithH bs              = Header slideLevel nullAttr [Str "\0"] : bs