private void indexAnnotation(Resource skos_concept, Document conceptDoc,
AnnotationProperty property, String field) {
StmtIterator stmt_iter = skos_concept.listProperties(property);
while (stmt_iter.hasNext()) {
Literal labelLiteral = stmt_iter.nextStatement().getObject()
.as(Literal.class);
String label = labelLiteral.getLexicalForm();
String labelLang = labelLiteral.getLanguage();
if (this.languages != null && !this.languages.contains(labelLang)) {