diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 1fd243008..fbfcf9c61 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -5,5 +5,8 @@ build:
   tools:
     python: "mambaforge-4.10"
 
+sphinx:
+  configuration: docs/conf.py
+
 conda:
   environment: docs/environment.yml
diff --git a/CHANGES.rst b/CHANGES.rst
index 5e1f2506b..e4bcda2ba 100755
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,6 +1,14 @@
 Changelog
 =========
 
+Version 8.3.1
+~~~~~~~~~~~~~
+
+Bug fix release:
+
+All changes:
+https://github.com/Open-MSS/MSS/milestone/99?closed=1
+
 Version 8.3.0
 ~~~~~~~~~~~~~
 
diff --git a/docs/conf.py b/docs/conf.py
index 3204f3761..edaea685c 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -119,7 +119,7 @@ def get_tutorial_images():
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = []
+extensions = ['sphinx_rtd_theme']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
@@ -217,23 +217,19 @@ def get_tutorial_images():
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-#html_theme = 'sphinx_rtd_theme'
+html_theme = 'sphinx_rtd_theme'
 
 if not on_rtd:  # only import and set the theme if we're building docs locally
     import sphinx_rtd_theme
-    html_theme = 'sphinx_rtd_theme'
     html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
     html_style = 'css/mss.css'
 else:
+    htmls_static_path = ['_static']
+    html_css_files = ['mss.css']
     html_context = {
         'display_github': False, # Add 'Edit on Bitbucket' link instead of 'View page source'
         'last_updated': True,
         'commit': False,
-        'css_files': [
-            'https://media.readthedocs.org/css/sphinx_rtd_theme.css',
-            'https://media.readthedocs.org/css/readthedocs-doc-embed.css',
-            '_static/css/mss.css',
-        ],
     }
 
 # Theme options are theme-specific and customize the look and feel of a theme
diff --git a/docs/publications.rst b/docs/publications.rst
index 68aa927be..c563a6d88 100644
--- a/docs/publications.rst
+++ b/docs/publications.rst
@@ -24,9 +24,11 @@ Acknowledgement
 
 Please add the following acknowledgement and cite to your publications:
 
+
   The authors gratefully acknowledge the use of the MSS flight planning
-  software (Rautenhaus, 2012; MSS development was partially funded by
-  the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)
-  project no. UN 311/3-1)“.
+  software (Bauer et al, 2022, Rautenhaus et al, 2012;
+  MSS development was partially funded by the Deutsche Forschungsgemeinschaft
+  (DFG, German Research Foundation) project no. UN 311/3-1
+  and project no. SPP 1294 423229456)
 
 Thank you very much.
diff --git a/mslib/index.py b/mslib/index.py
index 340fe9cd3..9ba7ddcb3 100644
--- a/mslib/index.py
+++ b/mslib/index.py
@@ -174,7 +174,7 @@ def plots():
                       "For further info on how to generate it, run the " \
                       "<b>gallery --help</b> command line parameter of mswms.<br>" \
                       "An example of the gallery can be seen " \
-                      "<a href=\"https://mss.readthedocs.io/en/latest/gallery/index.html\">here</a>"
+                      "<a href=\"https://mss.readthedocs.io/en/stable/gallery/index.html\">here</a>"
         return render_template("/content.html", act="plots", content=content)
 
     @APP.route("/mss/code/<path:filename>")
diff --git a/mslib/msui/multilayers.py b/mslib/msui/multilayers.py
index 08b494274..8c13cabfd 100644
--- a/mslib/msui/multilayers.py
+++ b/mslib/msui/multilayers.py
@@ -636,6 +636,9 @@ def _parse_vtimes(self):
             self.vtime_name = valid_time_names[0]
             values = self.extents[self.vtime_name]["values"]
             self.allowed_valid_times = sorted(self.parent.dock_widget.parse_time_extent(values))
+            while len(self.allowed_valid_times) > 1000:
+                logging.warning("Too many valid times (%s). discarding 90%%.", len(self.allowed_valid_times))
+                self.allowed_valid_times = self.allowed_valid_times[::10]
             self.vtimes = [_time.isoformat() + "Z" for _time in self.allowed_valid_times]
             if len(self.allowed_valid_times) == 0:
                 logging.error("Cannot determine valid time format of %s for %s", self.header.text(0), self.text(0))
diff --git a/mslib/msui/wms_control.py b/mslib/msui/wms_control.py
index e53270926..e793bc813 100644
--- a/mslib/msui/wms_control.py
+++ b/mslib/msui/wms_control.py
@@ -1285,7 +1285,7 @@ def normalize_crs(crs):
             if ret == QtWidgets.QMessageBox.Ignore:
                 self.check_for_allowed_crs = False
             elif ret == QtWidgets.QMessageBox.No:
-                return
+                return []
 
         # get...Time() will return None if the corresponding checkboxes are
         # disabled. <None> objects passed to wms.getmap will not be included
diff --git a/mslib/utils/config.py b/mslib/utils/config.py
index c740c220e..af9a918e5 100644
--- a/mslib/utils/config.py
+++ b/mslib/utils/config.py
@@ -111,8 +111,9 @@ class MSUIDefaultConfig:
     # URLs of default WMS servers.
     default_WMS = [
         "http://localhost:8081/",
-        "http://eumetview.eumetsat.int/geoserver/wms",
-        "https://apps.ecmwf.int/wms/?token=public"
+        "https://view.eumetsat.int/geoserver/wms",
+        "http://eccharts.ecmwf.int/wms/?token=public",
+        "https://neo.gsfc.nasa.gov/wms/wms"
     ]
 
     default_VSEC_WMS = [
diff --git a/mslib/utils/coordinate.py b/mslib/utils/coordinate.py
index b645fe5ec..54ecb2ff0 100644
--- a/mslib/utils/coordinate.py
+++ b/mslib/utils/coordinate.py
@@ -110,15 +110,13 @@ def rotate_point(point, angle, origin=(0, 0)):
 def get_projection_params(proj):
     proj = proj.lower()
     if proj.startswith("crs:"):
-        raise ValueError("CRS not supported")
-
         projid = proj[4:]
         if projid == "84":
             proj_params = {
                 "basemap": {"projection": "cyl"},
                 "bbox": "degree"}
         else:
-            raise ValueError("unsupported CRS code: '%s'", proj)
+            raise ValueError("Only CRS code 84 is supported: '%s' given", proj)
 
     elif proj.startswith("auto:"):
         raise ValueError("AUTO not supported")
diff --git a/mslib/utils/time.py b/mslib/utils/time.py
index 00d38f6a2..22b020013 100644
--- a/mslib/utils/time.py
+++ b/mslib/utils/time.py
@@ -43,7 +43,10 @@ def parse_iso_datetime(string):
 
 
 def parse_iso_duration(string):
-    return isodate.parse_duration(string)
+    try:
+        return isodate.parse_duration(string)
+    except isodate.ISO8601Error:
+        return datetime.timedelta(weeks=4)
 
 
 JSEC_START = datetime.datetime(2000, 1, 1)
diff --git a/mslib/version.py b/mslib/version.py
index 877b16c9e..642cdf5d0 100644
--- a/mslib/version.py
+++ b/mslib/version.py
@@ -24,4 +24,4 @@
     See the License for the specific language governing permissions and
     limitations under the License.
 """
-__version__ = u'8.3.0'
+__version__ = u'8.3.1'
diff --git a/requirements.d/development.txt b/requirements.d/development.txt
index 366ddaed2..e57232b2b 100644
--- a/requirements.d/development.txt
+++ b/requirements.d/development.txt
@@ -24,3 +24,5 @@ eventlet>0.30.2
 dnspython>=2.0.0, <2.3.0
 gsl==2.7.0
 boa
+xmlschema<2.5.0
+
diff --git a/tests/_test_utils/test_coordinate.py b/tests/_test_utils/test_coordinate.py
index 5408ce48c..e38582aeb 100644
--- a/tests/_test_utils/test_coordinate.py
+++ b/tests/_test_utils/test_coordinate.py
@@ -60,7 +60,7 @@ def test_get_projection_params(self):
         with pytest.raises(ValueError):
             coordinate.get_projection_params('auto:42001')
         with pytest.raises(ValueError):
-            coordinate.get_projection_params('crs:84')
+            coordinate.get_projection_params('crs:83')
 
 
 class TestAngles(object):