diff --git a/dnet-ariadneplus-graphdb-publisher/src/main/resources/eu/dnetlib/ariadneplus/sparql/enrich/IAA/ordered_sparql_insert_IAA_sites.sparql b/dnet-ariadneplus-graphdb-publisher/src/main/resources/eu/dnetlib/ariadneplus/sparql/enrich/IAA/ordered_sparql_insert_IAA_sites.sparql
index c20c0fc..7ea6bdb 100644
--- a/dnet-ariadneplus-graphdb-publisher/src/main/resources/eu/dnetlib/ariadneplus/sparql/enrich/IAA/ordered_sparql_insert_IAA_sites.sparql
+++ b/dnet-ariadneplus-graphdb-publisher/src/main/resources/eu/dnetlib/ariadneplus/sparql/enrich/IAA/ordered_sparql_insert_IAA_sites.sparql
@@ -1,9 +1,5 @@
 ADD SILENT <https://ariadne-infrastructure.eu/api_________::ariadne_plus::iaa_survey::maps> TO <https://ariadne-infrastructure.eu/api_________::ariadne_plus::iaa_survey::sites>;
-DROP SILENT GRAPH <https://ariadne-infrastructure.eu/api_________::ariadne_plus::iaa_survey::maps>;
-
 ADD SILENT <https://ariadne-infrastructure.eu/api_________::ariadne_plus::iaa_survey::periods> TO <https://ariadne-infrastructure.eu/api_________::ariadne_plus::iaa_survey::sites>;
-DROP SILENT GRAPH <https://ariadne-infrastructure.eu/api_________::ariadne_plus::iaa_survey::periods>;
-
 
 PREFIX aocat: <https://www.ariadne-infrastructure.eu/resource/ao/cat/1.1/>
 PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
@@ -233,8 +229,10 @@ PREFIX  aocat: <https://www.ariadne-infrastructure.eu/resource/ao/cat/1.1/>
  WHERE {
      GRAPH <https://ariadne-infrastructure.eu/api_________::ariadne_plus::iaa_survey::sites> {
          ?temporal aocat:has_native_period ?nativePeriod .
+         optional{
          ?temporal aocat:from ?temporalFrom .
          ?temporal aocat:until ?temporalUntil .
+         }
      }
 
  };
@@ -250,6 +248,7 @@ PREFIX  aocat: <https://www.ariadne-infrastructure.eu/resource/ao/cat/1.1/>
  WHERE {
      GRAPH <https://ariadne-infrastructure.eu/api_________::ariadne_plus::iaa_survey::sites> {
          ?temporal aocat:has_native_period ?nativePeriod .
-         ?nativePeriod rdfs:label ?periodLabel .
+         ?nativePeriod skos:prefLabel ?periodLabel .
      }
- };
\ No newline at end of file
+ };
+