A search on clinical trials brings up drop down menus under the refine results. This is a feature of the Google Co-op, topics platform of the program. This is the first time I have seen drop down menus used in part of the Google refinement feature. Here is a screen capture:
![refine-google-drop-downs.png](https://www.seroundtable.com/archives/refine-google-drop-downs.png)
Interesting stuff.
Forum discussion at Search Engine Watch Forums.