improve documentation thanks @jerome

README.md

@@ -40,8 +40,11 @@ rJS(window)
   });
 ```
 
-In parent gadget downloadJSON() can be declared. DownloadJSON() can be used to
-fetch schema from jio storage. Example:
+In parent gadget downloadJSON() can be declared. downloadJSON() can be used to
+fetch schema from [jio storage](https://jio.nexedi.com/). Gadget runs downloadJSON()
+for fetching schema if schema_url starts with `urn:jio:` but path absolutisation works 
+only for `urn:jio:reference?`. Example which demonstrates how a schema can be fetched
+from jio storage:
 
 ```javascript
 rJS(window)
@@ -50,11 +53,25 @@ rJS(window)
       url = arr[0],
       reference,
       args;
-    //   return g.jio_getAttachment(id, "data", {format: "json"});
     if (url.startsWith("urn:jio:reference?")) {
       reference = decodeURIComponent(url.replace("urn:jio:reference?", ""));
       args = {
-        query: '(portal_type: "JSON Schema") AND ((reference: "' + reference + '"))',
+        query: Query.objectToSearchText({
+                   type: "complex",
+                   operator: "AND",
+                   query_list: [
+                     {
+                       key: "portal_type",
+                       type: "simple",
+                       value: "JSON Schema"
+                     },
+                     {
+                       key: "reference",
+                       type: "simple",
+                       value: reference
+                     }
+                   ]
+                 }),
         limit: [0, 1],
         select_list: [],
         sort_on: [["modification_date", "descending"]]