Replaced OLA and VisOn links by softwareheritage ones

html/impl.html

@@ -127,7 +127,7 @@ Proc. 3rd Ontology matching workshop, Karlsruhe (DE), pp214-218, 2008
 <br /><small></small-->
 </dd>
 
-<dt>[<a href="http://VisOn.gforge.inria.fr">VisOn</a>] (the link will be disabled soon, 2021)</dt>
+<dt>[<a href="https://archive.softwareheritage.org/swh:1:snp:df45fb3b9f948d75ea34a45fdbbd8bc742c03bc5;origin=svn://scm.gforge.inria.fr/svnroot/vison/">VisOn</a>] <!--the link http://VisOn.gforge.inria.fr be disabled soon, 2021--></dt>
 <dd>The VisOn ontology visualizer now works with any implementation of the API.
 It provides the opportunity to load and display ontologies, load, run, display and compare alignment algorithms.</dd>
 
@@ -488,7 +488,7 @@ Proc. 13th Ontology matching workshop, Monterey (CA, US), pp25-36, 2018
 <p>These systems usually implement some matching algorithm on top of the API implementation (and benefit from all implemented services).</p>
 
 <dl>
-<dt>[<a href="http://ola.gforge.inria.fr">OLA</a>] (the link will be disabled soon, 2021)</dt>
+<dt>[<a href="https://archive.softwareheritage.org/swh:1:snp:631bf1944d2180293e1f60b656dcd08826834cae;origin=svn://scm.gforge.inria.fr/svnroot/ola/">OLA</a>] <!--the link http://ola.gforge.inria.fr will be disabled soon, 2021--></dt>
 <dd>A matching algorithm for OWL-Lite that measures distance between all ontology components and perform an iterative fixpoint search.
 <br /><small>
 Jean-Fran&ccedil;ois Djoufak-Kengue, Jérôme Euzenat, Petko Valtchev,