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https://www.wikidata.org/wiki/Wikidata:Contact_the_development_team#New_API_wbeditentity:_Help

           "references": [
               {
                   "snaks": [
                       {
                           "snaktype": "value",
                           "property": "P17",
                           "datavalue": {
                               "value": {
                                   "entity-type": "item",
                                   "numeric-id": 144
                               },
                               "type": "wikibase-entityid"
                           }
                       }
                   ]
               }
           ]
will not work
        "references":[
           {
              "snaks":{
                 "P56":[
                    {
                       "snaktype":"value",
                       "property":"P56",
                       "datavalue":{
                          "value":"src",
                          "type":"string"
                       }
                    }
                 ]
              }
           }
        ]
will work

Both of the above should probably work for both references and qualifiers