diff --git a/README.md b/README.md
index ab0b681..a5e1cbd 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,8 @@ Reference (module for Omeka S)
 alphabetized index) of links to records or to searches for all resources classes
 (item types) and properties (metadata fields) of all resources of an Omeka S
 instance, or an expandable hierarchical tree of statically specified references.
-These lists can be displayed in any page via a helper or a block.
+These lists can be displayed in any page via a helper or a block. References can
+be limited by site or any other pool, and ordered alphabetically or by count.
 
 This [Omeka S] module is a rewrite of the [Reference plugin] for [Omeka] and
 intends to provide the same features as the original plugin.
@@ -77,6 +78,8 @@ echo $this->reference()->displayListForTerm($term,
     [
         'type' => 'properties',
         'resource_name' => 'items',
+        'order' => ['alphabetic' => 'ASC'],
+        'query' => ['site_id' => 1],
         'per_page' => null,
         'page' => null,
     ],
@@ -99,6 +102,7 @@ echo $this->reference()->displayTree($references,
         'term' => $term,
         'type' => 'properties',
         'resource_name' => 'items',
+        'query' => ['site_id' => 1],
     ],
     [
         'query_type' => 'eq',
@@ -115,6 +119,12 @@ echo $this->reference()->displayTree($references,
 All arguments are optional and the default ones are set in the config page or in
 the block, but they can be overridden in the theme.
 
+For `order`, the sort can be `['count' => 'DESC']` too.
+
+For `query`, it is the standard query used in the api of Omeka, or the arguments
+taken from the url of an advanced search, converted into an array with `parse_str`.
+The conversion is automatically done inside the user interface (page blocks).
+
 
 Warning
 -------
diff --git a/src/Controller/Site/ReferenceController.php b/src/Controller/Site/ReferenceController.php
index 594d40d..c02564a 100644
--- a/src/Controller/Site/ReferenceController.php
+++ b/src/Controller/Site/ReferenceController.php
@@ -58,11 +58,12 @@ public function listAction()
         $term = $slugData['term'];
         $type = $slugData['type'];
         $resourceName = $settings->get('reference_resource_name', 'resources');
+        $order = ['value.value' => 'ASC'];
         $query = ['site_id' => $this->currentSite()->id()];
 
         $output = $this->params()->fromQuery('output');
         if ($output === 'json') {
-            $references = $this->reference()->getList($term, $type, $resourceName, $query);
+            $references = $this->reference()->getList($term, $type, $resourceName, $order, $query);
             $view = new JsonModel($references);
             return $view;
         }
@@ -76,6 +77,7 @@ public function listAction()
         $view->setVariable('args', [
             'type' => $type,
             'resource_name' => $resourceName,
+            'order' => $order,
             'query' => $query,
         ]);
         $view->setVariable('options', [
diff --git a/src/Form/ReferenceBlockForm.php b/src/Form/ReferenceBlockForm.php
index 693e2d6..b8e0d1c 100644
--- a/src/Form/ReferenceBlockForm.php
+++ b/src/Form/ReferenceBlockForm.php
@@ -92,6 +92,19 @@ public function init()
                 ],
             ],
         ]);
+        $referenceFieldset->add([
+            'name' => 'order',
+            'type' => Element\Select::class,
+            'options' => [
+                'label' => 'Select order', // @translate
+                'value_options' => [
+                    'alphabetic ASC' => 'Alphabetic ascendant',  // @translate
+                    'alphabetic DESC' => 'Alphabetic descendant',  // @translate
+                    'count ASC' => 'Count ascendant',  // @translate
+                    'count DESC' => 'Count descendant',  // @translate
+                ],
+            ],
+        ]);
         $referenceFieldset->add([
             'name' => 'query',
             'type' => Element\Text::class,
diff --git a/src/Mvc/Controller/Plugin/Reference.php b/src/Mvc/Controller/Plugin/Reference.php
index 48d30e1..e7d812b 100644
--- a/src/Mvc/Controller/Plugin/Reference.php
+++ b/src/Mvc/Controller/Plugin/Reference.php
@@ -45,18 +45,20 @@ public function __construct(EntityManager $entityManager, Api $api)
      * @param int|string|PropertyRepresentation|ResourceClassRepresentation $term
      * @param string $type "properties" (default) or "resource_classes".
      * @param string $resourceName All resources types if empty.
+     * @param array $order Sort and direction: ['alphabetic' => 'ASC'] (default),
+     * ['count' => 'DESC'], or any available column as sort.
      * @param array $query An api search formatted query to limit results.
      * @param int $perPage
      * @param int $page One-based page number.
      * @return Reference|array|null The result or null if called directly, else
      * this view plugin.
      */
-    public function __invoke($term = null, $type = null, $resourceName = null, $query = null, $perPage = null, $page = null)
+    public function __invoke($term = null, $type = null, $resourceName = null, $order = null,$query = null, $perPage = null, $page = null)
     {
         if (empty($term)) {
             return $this;
         }
-        return $this->getList($term, $type, $resourceName, $query, $perPage, $page);
+        return $this->getList($term, $type, $resourceName, $order, $query, $perPage, $page);
     }
 
     /**
@@ -65,12 +67,14 @@ public function __invoke($term = null, $type = null, $resourceName = null, $quer
      * @param int|string|PropertyRepresentation|ResourceClassRepresentation $term
      * @param string $type "properties" (default) or "resource_classes".
      * @param string $resourceName
+     * @param array $order Sort and direction: ['alphabetic' => 'ASC'] (default),
+     * ['count' => 'DESC'], or any available column as sort.
      * @param array $query An api search formatted query to limit results.
      * @param int $perPage
      * @param int $page One-based page number.
      * @return array Associative array with total and first record ids.
      */
-    public function getList($term, $type = null, $resourceName = null, $query = null, $perPage = null, $page = null)
+    public function getList($term, $type = null, $resourceName = null, $order = null, $query = null, $perPage = null, $page = null)
     {
         $type = $type === 'resource_classes' ? 'resource_classes' : 'properties';
 
@@ -84,7 +88,7 @@ public function getList($term, $type = null, $resourceName = null, $query = null
             return;
         }
 
-        $references = $this->getReferencesList($termId, $type, $entityClass, $query, [], $perPage, $page, null);
+        $references = $this->getReferencesList($termId, $type, $entityClass, $order, $query, [], $perPage, $page, null);
         return $references;
     }
 
@@ -273,7 +277,7 @@ public function count($term, $type = null, $resourceName = null, $query = null)
      *
      * @param int|string|PropertyRepresentation|ResourceClassRepresentation $term
      * @param array $args Specify the references with "type", "resource_name",
-     * "query", "per_page" and "page".
+     * "order", "query", "per_page" and "page".
      * @param array $options Options to display references. Values are booleans:
      * - raw: Show references as raw text, not links (default to false)
      * - skiplinks: Add the list of letters at top and bottom of the page
@@ -302,12 +306,13 @@ public function displayListForTerm($term, array $args = [], array $options = [])
 
         $options = $this->cleanOptions($options);
 
+        $order = empty($args['order']) ? null : $args['order'];
         $query = empty($args['query']) ? null : $args['query'];
         $perPage = empty($args['per_page']) ? null : (int) $args['per_page'];
         $page = empty($args['page']) ? null : (int) $args['page'];
         $output = $options['link_to_single'] ? 'withFirst' : 'list';
 
-        $references = $this->getReferencesList($termId, $type, $entityClass, $query, [], $perPage, $page, $output);
+        $references = $this->getReferencesList($termId, $type, $entityClass, $order, $query, [], $perPage, $page, $output);
 
         $controller = $this->getController();
         $partial = $controller->viewHelpers()->get('partial');
@@ -317,6 +322,7 @@ public function displayListForTerm($term, array $args = [], array $options = [])
             'type' => $type,
             'resourceName' => $resourceName,
             'options' => $options,
+            'order' => $order,
             'query' => $query,
             'perPage' => $perPage,
             'page' => $page,
@@ -432,7 +438,7 @@ public function displayTree($references, array $args, array $options = [])
                 $branches[] = $branch;
                 $lowerBranches[] = $hasMb ? mb_strtolower($branch) : strtolower($branch);
             }
-            $totals = $this->getReferencesList($termId, $type, $entityClass, $query, $lowerBranches, null, null, $output);
+            $totals = $this->getReferencesList($termId, $type, $entityClass, null, $query, $lowerBranches, null, null, $output);
         }
         // Simple tree.
         else {
@@ -443,7 +449,7 @@ public function displayTree($references, array $args, array $options = [])
                 : array_map(function($v) {
                     return strtolower(key($v));
                 }, $references);
-            $totals = $this->getReferencesList($termId, $type, $entityClass, $query, $lowerReferences, null, null, $output);
+            $totals = $this->getReferencesList($termId, $type, $entityClass, null, $query, $lowerReferences, null, null, $output);
         }
 
         $lowerTotals = [];
@@ -557,6 +563,8 @@ protected function cleanOptions($options)
      * @param int $termId May be the resource class id.
      * @param string $type "properties" (default) or "resource_classes".
      * @param string $entityClass
+     * @param array $order Sort and direction: ['alphabetic' => 'ASC'] (default),
+     * ['count' => 'DESC'], or any available column as sort.
      * @param array $query An api search formatted query to limit results.
      * @param array $values Allow to limit the answer to the specified values.
      * @param int $perPage
@@ -569,6 +577,7 @@ protected function getReferencesList(
         $termId,
         $type,
         $entityClass,
+        $order = null,
         $query = null,
         $values = [],
         $perPage = null,
@@ -602,8 +611,7 @@ protected function getReferencesList(
                     ->where($qb->expr()->eq('resource.resourceClass', ':resource_class'))
                     ->setParameter('resource_class', (int) $resourceClassId)
                     ->groupBy('value.value')
-                    ->orderBy('value.value', 'ASC')
-                    ->addOrderBy('resource.id', 'ASC');
+                ;
 
                 if ($entityClass !== \Omeka\Entity\Resource::class) {
                     $qb
@@ -628,11 +636,35 @@ protected function getReferencesList(
                     // Only literal values.
                     ->andWhere($qb->expr()->isNotNull('value.value'))
                     ->groupBy('value.value')
-                    ->orderBy('value.value', 'ASC')
-                    ->addOrderBy('resource.id', 'ASC');
+                ;
                 break;
         }
 
+        if ($order) {
+            $direction = reset($order);
+            $order = strtolower(key($order));
+            switch ($order) {
+                case 'count':
+                    $qb
+                        ->orderBy('total', $direction)
+                        // Add alphabetic order for ergonomy.
+                        ->addOrderBy('value.value', 'ASC');
+                    break;
+                case 'alphabetic':
+                    $order = 'value.value';
+                    // No break;
+                default:
+                    $qb
+                        ->orderBy($order, $direction);
+            }
+        } else {
+            $qb
+                ->orderBy('value.value', 'ASC');
+        }
+        // Always add an order by id for consistency.
+        $qb
+            ->addOrderBy('resource.id', 'ASC');
+
         if ($output === 'withFirst') {
             $qb
                 ->addSelect([
diff --git a/src/Site/BlockLayout/Reference.php b/src/Site/BlockLayout/Reference.php
index 92c0a73..730e82c 100644
--- a/src/Site/BlockLayout/Reference.php
+++ b/src/Site/BlockLayout/Reference.php
@@ -92,7 +92,13 @@ public function form(PhpRenderer $view, SiteRepresentation $site,
             ? $this->referencePlugin->convertLevelsToTree($data['reference']['tree'])
             : '';
 
-        $data['reference']['query'] = urldecode(http_build_query($data['reference']['query'], "\n", '&', PHP_QUERY_RFC3986));
+        $data['reference']['order'] = empty($data['reference']['order'])
+            ? 'alphabetic ASC'
+            : key($data['reference']['order']) . ' ' . reset($data['reference']['order']);
+
+        $data['reference']['query'] = is_array($data['reference']['query'])
+            ? urldecode(http_build_query($data['reference']['query'], "\n", '&', PHP_QUERY_RFC3986))
+            : $data['reference']['query'];
 
         // TODO Fix set data for radio buttons.
         $form->setData([
@@ -192,6 +198,10 @@ public function onHydrate(SitePageBlock $block, ErrorStore $errorStore)
             $data['reference']['resource_name'] = 'items';
         }
 
+        $data['reference']['order'] = empty($data['reference']['order'])
+            ? ['alphabetic' => 'ASC']
+            : [strtok($data['reference']['order'], ' ') => strtok(' ')];
+
         parse_str($data['reference']['query'], $query);
         $data['reference']['query'] = $query;
 
diff --git a/src/View/Helper/Reference.php b/src/View/Helper/Reference.php
index 9b4e769..4a6e859 100644
--- a/src/View/Helper/Reference.php
+++ b/src/View/Helper/Reference.php
@@ -27,18 +27,20 @@ public function __construct(ReferencePlugin $reference)
      * @param int|string|PropertyRepresentation|ResourceClassRepresentation $term
      * @param string $type "properties" (default) or "resource_classes".
      * @param string $resourceName All resources types if empty.
+     * @param array $order Sort and direction: ['alphabetic' => 'ASC'] (default),
+     * ['count' => 'DESC'], or any available column as sort.
      * @param array $query An api search formatted query to limit results.
      * @param int $perPage
      * @param int $page One-based page number.
      * @return Reference|array|null The result or null if called directly, else
      * this view helper.
      */
-     public function __invoke($term = null, $type = null, $resourceName = null, $query = null, $perPage = null, $page = null)
+     public function __invoke($term = null, $type = null, $resourceName = null, $order = null, $query = null, $perPage = null, $page = null)
      {
         if (empty($term)) {
             return $this;
         }
-        return $this->reference->getList($term, $type, $resourceName, $query, $perPage, $page);
+        return $this->reference->getList($term, $type, $resourceName, $order, $query, $perPage, $page);
     }
 
     /**
@@ -47,14 +49,16 @@ public function __invoke($term = null, $type = null, $resourceName = null, $quer
      * @param int|string|PropertyRepresentation|ResourceClassRepresentation $term
      * @param string $type "properties" (default) or "resource_classes".
      * @param string $resourceName
+     * @param array $order Sort and direction: ['alphabetic' => 'ASC'] (default),
+     * ['count' => 'DESC'], or any available column as sort.
      * @param array $query An api search formatted query to limit results.
      * @param int $perPage
      * @param int $page One-based page number.
      * @return array Associative array with total and first record ids.
      */
-    public function getList($term, $type = null, $resourceName = null, $query = null, $perPage = null, $page = null)
+    public function getList($term, $type = null, $resourceName = null, $order = null, $query = null, $perPage = null, $page = null)
     {
-        return $this->reference->getList($term, $type, $resourceName, $query, $perPage, $page);
+        return $this->reference->getList($term, $type, $resourceName, $order, $query, $perPage, $page);
     }
 
     /**
@@ -91,7 +95,7 @@ public function count($term, $type = null, $resourceName = null, $query = null)
      *
      * @param int|string|PropertyRepresentation|ResourceClassRepresentation $term
      * @param array $args Specify the references with "type", "resource_name",
-     * "query", "per_page" and "page".
+     * "order", "query", "per_page" and "page".
      * @param array $options Options to display references. Values are booleans:
      * - raw: Show references as raw text, not links (default to false)
      * - skiplinks: Add the list of letters at top and bottom of the page