diff --git a/detail/actions.cpp b/detail/actions.cpp
index a6e6f1a..074e05f 100644
--- a/detail/actions.cpp
+++ b/detail/actions.cpp
@@ -14,6 +14,7 @@
 #include <boost/filesystem/convenience.hpp>
 #include <boost/filesystem/fstream.hpp>
 #include <boost/lexical_cast.hpp>
+#include "./quickbook.hpp"
 #include "./actions.hpp"
 #include "./utils.hpp"
 #include "./markups.hpp"
diff --git a/detail/actions.hpp b/detail/actions.hpp
index 906776a..f18db05 100644
--- a/detail/actions.hpp
+++ b/detail/actions.hpp
@@ -41,9 +41,6 @@ namespace quickbook
     extern tm* current_time; // the current time
     extern tm* current_gm_time; // the current UTC time
     extern bool debug_mode;
-    extern unsigned qbk_major_version;
-    extern unsigned qbk_minor_version;
-    extern unsigned qbk_version_n; // qbk_major_version * 100 + qbk_minor_version
     extern std::vector<std::string> include_path;
 
     // forward declarations
diff --git a/detail/quickbook.cpp b/detail/quickbook.cpp
index 654162f..5cfe3fb 100644
--- a/detail/quickbook.cpp
+++ b/detail/quickbook.cpp
@@ -7,6 +7,7 @@
     License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
     http://www.boost.org/LICENSE_1_0.txt)
 =============================================================================*/
+#include "./quickbook.hpp"
 #include "./actions_class.hpp"
 #include "../block.hpp"
 #include "../doc_info.hpp"
diff --git a/detail/quickbook.hpp b/detail/quickbook.hpp
new file mode 100644
index 0000000..3aa8852
--- /dev/null
+++ b/detail/quickbook.hpp
@@ -0,0 +1,47 @@
+/*=============================================================================
+    Copyright (c) 2009 Daniel James
+    Copyright (c) 2002 2004 2006 Joel de Guzman
+    Copyright (c) 2004 Eric Niebler
+    http://spirit.sourceforge.net/
+
+    Use, modification and distribution is subject to the Boost Software
+    License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+    http://www.boost.org/LICENSE_1_0.txt)
+=============================================================================*/
+
+#if !defined(BOOST_SPIRIT_QUICKBOOK_QUICKBOOK_HPP)
+#define BOOST_SPIRIT_QUICKBOOK_QUICKBOOK_HPP
+
+namespace quickbook
+{
+    extern unsigned qbk_major_version;
+    extern unsigned qbk_minor_version;
+    extern unsigned qbk_version_n; // qbk_major_version * 100 + qbk_minor_version
+
+    struct quickbook_range {
+        template <typename Arg>
+        struct result
+        {
+            typedef bool type;
+        };
+        
+        quickbook_range(unsigned min, unsigned max)
+            : min(min), max(max) {}
+        
+        bool operator()() const {
+            return qbk_version_n >= min && qbk_version_n < max;
+        }
+
+        unsigned min, max;
+    };
+    
+    inline quickbook_range qbk_since(unsigned min) {
+        return quickbook_range(min, 999);
+    }
+    
+    inline quickbook_range qbk_before(unsigned max) {
+        return quickbook_range(0, max);
+    }
+}
+
+#endif
\ No newline at end of file
diff --git a/doc_info.hpp b/doc_info.hpp
index 0e7791d..7bab42c 100644
--- a/doc_info.hpp
+++ b/doc_info.hpp
@@ -11,6 +11,7 @@
 #define BOOST_SPIRIT_QUICKBOOK_DOC_INFO_HPP
 
 #include "./phrase.hpp"
+#include "./detail/quickbook.hpp"
 #include <boost/spirit/include/classic_core.hpp>
 #include <boost/spirit/include/classic_actor.hpp>
 #include <boost/spirit/include/classic_loops.hpp>
@@ -19,8 +20,6 @@
 namespace quickbook
 {
     using namespace boost::spirit::classic;
-    extern unsigned qbk_major_version;
-    extern unsigned qbk_minor_version;
 
     template <typename Actions>
     struct doc_info_grammar