To refine the search combine search terms with Boolean operators AND, OR, NOT:

- drones AND quadcopters
Finds publications containing both words. 

- drones OR quadcopters
Finds publications containing at least one of the two words. 

- drones NOT quadcopters 
Finds publications containing only the first but not the second word. 

In full-text search use quotation marks to search for an exact phrase:
- "unmanned vehicles"
Finds publications containing exactly the same words in the same order.

If necessary, specify a collection. By default, all collections are selected.