add entry for 2.3.1
diff --git a/Doc/texinputs/license.tex b/Doc/texinputs/license.tex
index a47a44e..5e325a9 100644
--- a/Doc/texinputs/license.tex
+++ b/Doc/texinputs/license.tex
@@ -41,6 +41,7 @@
   \linev{2.2.2}{2.2.1}{2002}{PSF}{yes}
   \linev{2.2.3}{2.2.2}{2002-2003}{PSF}{yes}
   \linev{2.3}{2.2.2}{2002-2003}{PSF}{yes}
+  \linev{2.3.1}{2.3}{2002-2003}{PSF}{yes}
 \end{tablev}
 
 \note{GPL-compatible doesn't mean that we're distributing