update readme

Author: audemard

README.md

@@ -27,12 +27,12 @@ These problems/models mainly come from the literature/community, in particular f
 
 In order to find specific models from our repository, you can use:
 
-- [this page]() from PySCP3 website
-- use the Python script 'searchmodels.py', at the root of theb main directory, whose usage is:
+- [this page](http://pycsp.org/models/) from PySCP3 website
+- use the Python script 'searchmodels.py', at the root of the main directory, whose usage is:
 
 ```
-usage: python searchmodels.py [-constraint=Sum] [-tag=xcsp23] [-name='Bacp'] [-cop|csp]
-                              [-reverse] [-json|-file] [-showtags] [-showcontraints]
+usage: python searchmodels.py [-constraint=Sum] [-tag=xcsp23] [-name='Bacp'] [-cop|-csp]
+                              [-reverse] [-json|-dir|-gihub] [-showtags] [-showcontraints]
 
 Extract problems with respect to a given query.
 You can mix different queries resulting to all problems that matches all queries.
@@ -48,7 +48,8 @@ You can also reverse the results.
   -cop|-csp extract  cop or csp problems
   -reverse reverse the results
 
-  -json display results as a json file
+  -json display results in json format 
   -github display results as links to github project
+  -dir display results as directory location
 ```