Update MIGRATION.md

MIGRATION.md

@@ -1,15 +1,40 @@
-## Migration From Other Enterprise Search
+## Migration From Other Enterprise Search Systems
 
 ### Google Search Apliance/Google Mini
 
 Fess provides GSA-Compatible API.
-The endpoint is localhost:8080/gsa.
-GsaApiManager is [here](https://github.com/codelibs/fess/blob/master/src/main/java/org/codelibs/fess/api/gsa/GsaApiManager.java).
+To enable this API, set `web.api.gsa=true` to system.properties.
+The endpoint is localhost:8080/gsa. 
+Sending a search query to localhost:8080/gsa/?q=QUERY, GSA-compatible response is returned.
+
+For the more details, see [GsaApiManager](https://github.com/codelibs/fess/blob/master/src/main/java/org/codelibs/fess/api/gsa/GsaApiManager.java) implementation.
 
 ### Google Site Search/Google Custom Search
 
-See [JSON API](http://fess.codelibs.org/11.0/user/json-response.html).
-(We have a plan to provide Compatible API)
+Fess provides Site-Search script to help migrations from GSS/CSE.
+Using Site-Search script, you can replace existing GSS/CSE JavaScript codes with:
+
+```
+<script>
+  (function() {
+    var fess = document.createElement('script');
+    fess.type = 'text/javascript';
+    fess.async = true;
+    fess.src = '//<Fess Server Name>/js/ss/fess-ss.min.js';
+    fess.charset = 'utf-8';
+    fess.setAttribute('id', 'fess-ss');
+    fess.setAttribute('fess-url', '//<Server Name>/json');
+    var s = document.getElementsByTagName('script')[0];
+    s.parentNode.insertBefore(fess, s);
+  })();
+</script>
+<fess:search></fess:search>
+```
+
+Fess Site Search works as below:
+
+![Fess Site Search](http://fess.codelibs.org/_images/fess-ss-1.png "Fess Site Search")
+
 
 ### Others