Apply style to administration interface I would like to do a minor change to the form in which articles are added, it's just a few lines of CSS. However drupal doesn't seem to load the stylesheets of my theme if the admin interface is used in non-overlay mode.

So is there a way to add CSS to the administration interface without touching the system stylesheets?
Without having to do too much you can use CSS Injector: https://www.drupal.org/project/css_injector

Just install the module and then make your CSS rule to only work on the assigned admin theme. 

There are of course other ways to do this, you can write a custom module and add CSS that way as well.