*
* Use the \ref gras_userdata_new macro to create a new user data (or malloc it
* and use \ref gras_userdata_set yourself), and \ref gras_userdata_get to
- * retrieve a reference to it.
+ * retrieve a reference to it.
+ *
+ * For more info on this, you may want to check the relevant lesson of the GRAS tutorial:
+ * \ref GRAS_tut_tour_globals
*/
/* @{ */