diff --git a/doc/org/dstar2tgba.org b/doc/org/dstar2tgba.org
index c2b1651e9..e4e57e8bb 100644
--- a/doc/org/dstar2tgba.org
+++ b/doc/org/dstar2tgba.org
@@ -66,7 +66,7 @@ Acc-Sig:
 =dstar2tgba= can now be used to convert this DRA into a TGBA, a BA, or
 a Monitor, using the same options as [[file:ltl2tgba.org][=ltl2tgba=]].
 
-For instance here is the conversion to a Büchi automaton (=-B=) in [[http://http://www.graphviz.org/][GraphViz]]'s format:
+For instance here is the conversion to a Büchi automaton (=-B=) in [[http://www.graphviz.org/][GraphViz]]'s format:
 
 #+BEGIN_SRC sh :results verbatim :exports code
 dstar2tgba -B fagfb
diff --git a/doc/org/ltl2tgba.org b/doc/org/ltl2tgba.org
index 3d946f23f..5ceec39fb 100644
--- a/doc/org/ltl2tgba.org
+++ b/doc/org/ltl2tgba.org
@@ -42,7 +42,7 @@ assumed to be a formula to translate (this differs from [[file:ltlfilt.org][=ltl
 where such parameters are assumed to be filenames).
 
 =ltl2tgba= honors the [[file:oaut.org][common options for selecting the output format]].
-The default output format, as shown above, is [[http://http://www.graphviz.org/][GraphViz]]'s format.  This
+The default output format, as shown above, is [[http://www.graphviz.org/][GraphViz]]'s format.  This
 can converted into a picture, or into vectorial format using =dot= or
 =dotty=.  Typically, you could get a =pdf= of this TGBA using
 #+BEGIN_SRC sh :results verbatim :exports code
diff --git a/doc/org/ltl2tgta.org b/doc/org/ltl2tgta.org
index 563aa6627..f850de106 100644
--- a/doc/org/ltl2tgta.org
+++ b/doc/org/ltl2tgta.org
@@ -7,7 +7,7 @@ This tool generates various form of Testing Automata, i.e., automata
 that observe the /changes/ of atomic propositions, not their values.
 
 Three types of automata can be output.  The only output format
-supported currently is [[http://http://www.graphviz.org/][GraphViz]]'s format, with option =-8= to enable
+supported currently is [[http://www.graphviz.org/][GraphViz]]'s format, with option =-8= to enable
 UTF-8 characters as in other tools.
 
 The =--ta= option will translate a formula into Testing Automaton, as