diff --git a/README.md b/README.md
index 5175223..c8e0781 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ Windows and MAC OS X should be equally feasible. Note that the below
 instructions are written from a Linux/Ubuntu perspective, and probably
 need modifications for other platforms.
 
-Scyther is written partly in Python 2 (for the GUI, using wxPython) and
+Scyther is written partly in Python 3 (for the GUI, using wxPython) and
 partly in C (for the backend). 
 
 In order to run the tool from a repository checkout, it is required to
diff --git a/gui/INSTALL.md b/gui/INSTALL.md
index 41f49be..8b52c43 100644
--- a/gui/INSTALL.md
+++ b/gui/INSTALL.md
@@ -41,35 +41,20 @@ from the command line) then you need only the first.
 3. ### wxPython libraries ###
 
   The GUI user interface uses the wxPython libraries.
+  The recommended way of installing is through `pip` and described this page:
 
-	http://www.wxpython.org/download.php
+	https://www.wxpython.org/download.php
 
-  There are many different wxPython packages. You should choose a 32-bit
-  package that matches your Python version (e.g., 2.7). It is
-  recommended to select the unicode version from the stable releases.
+  This version of Scyther requires at least **wxPython 4.0**. Note that older versions of Scyther did not work with wxPython 4.
 
-  As of writing (May 2013) the following links lead to the appropriate
-  wxPython packages for Python 2.7:
-
-  *	**Windows**
-  
-   	http://downloads.sourceforge.net/wxpython/wxPython2.8-win32-unicode-2.8.12.1-py27.exe
-
-  *	**Mac OS X**
-  
-   	http://downloads.sourceforge.net/wxpython/wxPython2.8-osx-unicode-2.8.12.1-universal-py2.7.dmg
-
-   	Note that this package is in an old format and you will probably
-   	get a warning "Package is damaged". This can be resolved by:
-   	
-   	```
-   	 $ sudo installer -pkg /Volume/.../wxPython2.8-osx-unicode-universal-py2.7.pkg/ -target /
-   	```
-
-  *	**Ubuntu/Debian Linux**
-  
-   	http://wiki.wxpython.org/InstallingOnUbuntuOrDebian
+  For Ubuntu users, it is important to add an additional parameter, e.g., for Ubuntu 20.04, the recommended pip install is:
 
+  ```
+   $ sudo apt install python-pip
+   $ pip install -U \
+    -f https://extras.wxpython.org/wxPython4/extras/linux/gtk3/ubuntu-20.04 \
+    wxPython
+  ```
 
 Running Scyther
 ---------------
@@ -78,13 +63,13 @@ Extract the Scyther archive and navigate to the extracted directory.
 
 Start Scyther by executing the file
 
-  	scyther-gui.py
+  	`scyther-gui.py`
 
 in the main directory of the extracted archive.
 
   *	**Mac OS X**
   
-  	Right-click the file 'scyther-gui.py' and select "Open with" and
+  	Right-click the file `scyther-gui.py` and select "Open with" and
   	then "Python Launcher".
 
 
diff --git a/gui/Scyther/Scyther.py b/gui/Scyther/Scyther.py
index ba88f74..485bdf8 100755
--- a/gui/Scyther/Scyther.py
+++ b/gui/Scyther/Scyther.py
@@ -396,7 +396,6 @@ class Scyther(object):
         self.guessFileNames(spdl=spdl)
 
         # Generate temporary files for the output.
-        # Requires Python 2.3 though.
         (fde,fne) = tempfile.mkstemp()  # errors
         (fdo,fno) = tempfile.mkstemp()  # output
         if spdl:
diff --git a/gui/Scyther/XMLReader.py b/gui/Scyther/XMLReader.py
index 12514fc..b000957 100644
--- a/gui/Scyther/XMLReader.py
+++ b/gui/Scyther/XMLReader.py
@@ -37,7 +37,7 @@ import sys
 # Check for cElementTree presence. Otherwise use ElementTree.
 useiter = True
 try:
-    # python 2.5 has cElementTree in the core
+    # cElementTree is in Python since version 2.5
     import xml.etree.cElementTree as cElementTree
 except:
     # try the old way
diff --git a/gui/scyther-gui.py b/gui/scyther-gui.py
index 4edc894..6616ab2 100755
--- a/gui/scyther-gui.py
+++ b/gui/scyther-gui.py
@@ -35,7 +35,7 @@ interface of Scyther.
 The [wxPython] packages can be found at http://www.wxpython.org/
 
 Ubuntu users: the wxPython packages are called 'python-wxgtk' followed by the
-version number."""
+version number. This version of Scyther requires at least wxPython version 4.0."""
     elif ('32-bit mode' in str(err)) or ('no matching architecture' in str(err)):
         import os
 
@@ -92,7 +92,6 @@ The exact error was:
     """ % (errmsg,err))
 
 
-
 #---------------------------------------------------------------------------
 global WXPYTHON4
 global WXPYTHONINFREQ