Update extending.md

docs/user-documentation/extending.md

@@ -123,7 +123,7 @@ A tool that allows you to clone an existing content type. Can be used to copy an
 * [Entity Reference Integrity Extras](https://github.com/discoverygarden/entity_reference_integrity_extra)
 * [Entity Reference Purger](https://www.drupal.org/project/entity_reference_purger)
 
-Normally when deleting content (nodes, taxonomy terms, etc), any content that references the deleted entity isn't altered so you end up with orphan/zombie references, which are visible in the JSON representation but invisible otherwise. With Entity Reference Integrity's submodule (`entity_refefrence_integrity_enforce`), you won't be able to delete content that's referenced from elsewhere, preserving your database integrity.
+Normally when deleting content (nodes, taxonomy terms, etc), any content that references the deleted entity isn't altered so you end up with orphan/zombie references, which are visible in the JSON representation but invisible otherwise. With Entity Reference Integrity's submodule (`entity_reference_integrity_enforce`), you won't be able to delete content that's referenced from elsewhere, preserving your database integrity.
 
 Because the Drupal module doesn't play with Typed Relation fields, DGI's `entity_reference_integrity_extras` module is useful.