diff --git a/lib/asciidoctor-bibtex/version.rb b/lib/asciidoctor-bibtex/version.rb
index 7a92186..54c4d49 100644
--- a/lib/asciidoctor-bibtex/version.rb
+++ b/lib/asciidoctor-bibtex/version.rb
@@ -1,3 +1,3 @@
 module AsciidoctorBibtex
-  VERSION = '0.4.0'
+  VERSION = '0.4.1'
 end
diff --git a/lib/utils.rb b/lib/utils.rb
new file mode 100644
index 0000000..653e3a1
--- /dev/null
+++ b/lib/utils.rb
@@ -0,0 +1,111 @@
+# Some extension and helper methods. 
+#
+# Copyright (c) Peter Lane, 2012-13.
+# Copyright (c) Zhang YANG, 2016-09.
+# Released under Open Works License, 0.9.2
+
+module AsciidoctorBibtex
+  module Utils
+
+    def find_bibtex_database dir
+      begin
+        candidates = Dir.glob("#{dir}/*.bib")
+        if candidates.empty?
+          return ""
+        else
+          return candidates.first
+        end
+      rescue # catch all errors, and return empty string
+        return ""
+      end
+    end
+
+    # Used with numeric styles to combine consecutive numbers into ranges
+    # e.g. 1,2,3 -> 1-3, or 1,2,3,6,7,8,9,12 -> 1-3,6-9,12
+    # leave references with page numbers alone
+    def combine_consecutive_numbers str
+      nums = str.split(",").collect(&:strip)
+      res = ""
+      # Loop through ranges
+      start_range = 0
+      while start_range < nums.length do
+        end_range = start_range
+        while (end_range < nums.length-1 and
+               nums[end_range].is_i? and
+               nums[end_range+1].is_i? and
+               nums[end_range+1].to_i == nums[end_range].to_i + 1) do
+          end_range += 1
+        end
+        if end_range - start_range >= 2
+          res += "#{nums[start_range]}-#{nums[end_range]}, "
+        else
+          start_range.upto(end_range) do |i|
+            res += "#{nums[i]}, "
+          end
+        end
+        start_range = end_range + 1
+      end
+      # finish by removing last comma
+      res.gsub(/, $/, '')
+    end
+  end
+end
+
+module AsciidoctorBibtexArrayExtensions
+
+  # Retrieve the third item of an array
+  # Note: no checks for validity
+  def third
+    self[2]
+  end
+
+  # Join items in array using commas and 'and' on last item
+  def semantic_join
+    if size < 2
+      return self.join("")
+    end
+    result = ""
+    self.each_with_index do |item, index|
+      if index.zero?
+        result << item
+      elsif index == size-1
+        result << " and #{item}"
+      else
+        result << ", #{item}"
+      end
+    end
+
+    return result
+  end
+end
+
+# monkey patch the extension methods to Array
+class Array
+  include AsciidoctorBibtexArrayExtensions
+end
+
+# Converts html output produced by citeproc to asciidoc markup
+module StringHtmlToAsciiDoc
+  def html_to_asciidoc
+    r = self.gsub(/<\/?i>/, '_')
+    r = r.gsub(/<\/?b>/, '*')
+    r = r.gsub(/<\/?span.*?>/, '')
+    r = r.gsub(/\{|\}/, '')
+    r
+  end
+end
+
+# Provides a check that a string is in integer
+# Taken from:
+# http://stackoverflow.com/questions/1235863/test-if-a-string-is-basically-an-integer-in-quotes-using-ruby
+module IntegerCheck
+  def is_i?
+    !!(self =~ /^[-+]?[0-9]+$/)
+  end
+end
+
+# monkey patch the extension methods into String
+class String
+  include StringHtmlToAsciiDoc
+  include IntegerCheck
+end