This boolean is useful if you want to find out about the planet mars but not about the lander, for example. Use the NOT boolean to refine your search. Combinations Words, phrases and booleans can be used in combination. In fact, it is good practice to use quotes for all phrases. The capitalization of the booleans had been done previously for illustrative purposes.
Lower case is just as effective.
Thus with those two changes, our previous example would appear as follows. More than one boolean can be used at a time as well. Note how parenthesis are used to group the booleans together. Case Use case to be more specific. Once a the search button is clicked on or the 'Enter' key is pressed, the search engine performs the search and returns the results.