This is ESRI rest prj, "spatialReference":
{"wkt": "GEOGCS[\"GCS_WGS_1984\",DATUM[\"WGS84\",SPHEROID[\"WGS84\",6378137.0,298.257223563]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]]"}
Does anybody know what it should be in OpenLayers?