diff --git a/src/core/js/caosdb.js b/src/core/js/caosdb.js
index efc79764dbe9e7ea4760120598b892bb22eeb662..c6b3ce81c432c987c49a62e1fea8484b85d6bf2b 100644
--- a/src/core/js/caosdb.js
+++ b/src/core/js/caosdb.js
@@ -135,18 +135,19 @@ function getEntityRole(element) {
 }
 
 /**
- * Return the unit of element.
- * If the corresponding data-attribute can not be found undefined is returned.
- * @return A string containing the datatype of the element.
+ * Return the unit of entity or undefined.
+ *
+ * @param {HTMLElement} entity
+ * @return {String}
  */
-function getEntityUnit(element) {
-    var res = $(element).find("input.caosdb-f-entity-unit");
+function getEntityUnit(entity) {
+    var res = $(entity).find("input.caosdb-f-entity-unit");
     if (res.length == 1) {
         var x = res.val();
         return (x == '' ? undefined : x);
     }
 
-    return getEntityHeadingAttribute(element, "unit");
+    return getEntityHeadingAttribute(entity, "unit");
 }
 
 /**
diff --git a/src/core/js/form_elements.js b/src/core/js/form_elements.js
index d005dd8b494a96bcdefc7c7fde35190c0203f47e..0a492637bf2d9acb96917b17ef3eed8bf2f097e6 100644
--- a/src/core/js/form_elements.js
+++ b/src/core/js/form_elements.js
@@ -199,13 +199,19 @@ var form_elements = new function () {
         /**
          * Return SELECT form element with entity references.
          *
-         * The OPTIONS have the entities' ids as values and a description which
-         * is generated by a `make_desc` call-back function. If `make_desc` is
-         * undefined, the ids are shown instead.
+         * The OPTIONS' values are generated by the `make_value` call-back
+         * function from the entities. If `make_value` is undefined the
+         * entities' ids are used as values. The description which is generated
+         * by a `make_desc` call-back function. If `make_desc` is undefined,
+         * the ids are shown instead.
          *
          * @param {HTMLElement[]} entities - an array with entity elements.
          * @param {function} [make_desc] - a call-back function with one
-         *      parameter.
+         *      parameter which is an entity in HTML representation.
+         * @param {function} [make_value] - a call-back function with one
+         *      parameter which is an entity in HTML representation.
+         * @param {boolean} [multiple] - whether the select allows multiple
+         *      options to be selected.
          * @returns {HTMLElement} SELECT element with entity options.
          */
         this.make_reference_select = async function (entities, make_desc,