org: link to tl.pdf

* doc/org/index.org, doc/org/ioltl.org: Add links.

doc/org/index.org

@@ -34,9 +34,10 @@ The latest version is *{{{LASTRELEASE}}}* and was released on
 
 * Documentation
 
-- [[file:tools.org][Command-line tools]]
-- [[file:tut.org][Code examples]]
+- [[file:tools.org][Command-line tools]].
+- [[file:tut.org][Code examples]].
 - [[http://spot.lrde.epita.fr/doxygen/][Doxygen documentation]], generated automatically from the source code.
+- [[https://spot.lrde.epita.fr/tl.pdf][Definition of the temporal operators supported by Spot]].
 
 * On-line LTL/PSL translator
 

doc/org/ioltl.org

@@ -55,8 +55,8 @@ to express the same formula for different tools.
 Spot's default LTL parser will understand all of them.
 
 For a complete definition of the supported operators, including PSL
-operators, please refer to the =doc/tl/tl.pdf= document inside the
-Spot distribution.
+operators, please refer to the
+[[https://spot.lrde.epita.fr/tl.pdf][=doc/tl/tl.pdf= document inside the Spot distribution]].
 
 For Spot, an atomic proposition is any alphanumeric string that does
 not start with the (upper case) characters =F=, =G=, or =X=.  For