diff --git a/src/core/js/form_elements.js b/src/core/js/form_elements.js
index 0a492637bf2d9acb96917b17ef3eed8bf2f097e6..003445399498558c86017984b3c0d5da544532bf 100644
--- a/src/core/js/form_elements.js
+++ b/src/core/js/form_elements.js
@@ -243,15 +243,47 @@ var form_elements = new function () {
             return ret[0];
         }
 
+        /**
+         * @typedef {option} ReferenceDropDownConfig
+         *
+         * Configuration object for a drop down menu for selecting references.
+         * `make_reference_drop_down` generates such a drop down menu using a
+         * SELECT input with the references as its OPTION elements.
+         *
+         * The `query` parameter contains a query which is executed. The
+         * resulting entities are used to generate the OPTIONs.
+         *
+         * 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.
+         *
+         * The generated HTMLElements also contain a LABEL tag showing the text
+         * defined by `label`. If the `label` property is undefined, the `name`
+         * is shown instead.
+         *
+         * @property {string} name - The name of the select input.
+         * @property {string} query - Query for entities.
+         * @property {function} [make_value] - Call-back for the generation of
+         *     the OPTIONs' values from the entities.
+         * @property {function} [make_desc] - Call-back for the generation of
+         *     the OPTIONs' description from the entities.
+         * @property {boolean} [multiple] - Whether it is possible to select
+         *     multiple options at once.
+         * @property {string} [value] - Pre-selected value of the SELECT.
+         * @property {string} [label] - LABEL text.
+         * @property {string} [type] - This should be "reference_drop_down" or
+         *     undefined. This property is used by `make_form_field` to decide
+         *     which type of field is to be generated.
+         *
+         */
 
         /**
          * Search and retrieve entities and create a SELECT from element.
          *
-         * 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.
-         *
-         * @param {object} config
+         * @param {ReferenceDropDownConfig} config - all necessary parameters
+         *     for the configuration.
          * @returns {HTMLElement} SELECT element.
          */
         this.make_reference_drop_down = function (config) {