$all_nodes = db_select('node','e')->fields('e',array('nid','type'));
$all_nodes->addField('e','nid');
$all_nodes->condition('type','author');
$data = $all_nodes->execute();
$the_result = $data->fetchAll(PDO::FETCH_ASSOC);

foreach ($the_result as $node){
     $node_load =  DrupalnodeEntityNode::load($node['nid']);
     foreach ($node_load->field_institution_with_date as $item) {
        $the_entity_id = $item->entity->id();
     }
}