diff --git a/doc/conf.py b/doc/conf.py
index f21d2dc7..65462ead 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -11,8 +11,8 @@
 
 project = u'urbs'
 copyright = u'2014, tum-ens'
-version = '0.3'
-release = '0.3'
+version = '0.4'
+release = '0.4'
 
 exclude_patterns = ['_build']
 #pygments_style = 'sphinx'
diff --git a/doc/index.rst b/doc/index.rst
index 0a016978..acbda413 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -55,8 +55,18 @@ Features
 Changes
 -------
 
-Changes from version 0.2 to 0.3
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+2015-07-29 Version 0.4
+^^^^^^^^^^^^^^^^^^^^^^
+
+* Additional commodity types `Buy` and `Sell`, which support time-dependent 
+  prices.
+* Persistence functions `load` and `save`, based on pickle, allow saving
+  and retrieving input data and problem instances including results, for later
+  re-plotting or re-analysis without having to solve them again.
+* Documenation: `workflow`_ tutorial added with example "Newsealand"
+
+2014-12-05 Version 0.3
+^^^^^^^^^^^^^^^^^^^^^^
 
 * Processes now support multiple inputs and multiple output commodities.
 * As a consequence :func:`plot` now plots commodity balance by processes, not 
diff --git a/urbs.py b/urbs.py
index b8a86adf..dfbf9c09 100644
--- a/urbs.py
+++ b/urbs.py
@@ -16,6 +16,7 @@
 from datetime import datetime
 from operator import itemgetter
 from random import random
+from xlrd import XLRDError
 
 COLORS = {
     'Biomass plant': (0, 122, 55),