NOT excludes keywords. It must be used with AND. A search for Sustainable AND NOT development will return URL's for documents that that contain the word "Development" but not the word "Sustainable". That search would leave out all the references to sustainable that get it the way of our searches.

+/- You can use + for AND, - for AND NOT. For Sustainable AND Development you could write +Sustainable+Development.

Note you must put the arithmetic sign in front of each and leave no spaces.