You can search Credo Reference with a powerful Key Word search. This will examine every word on every page of every book and return results based on relevancy. Since this will probably retrieve far more than you need, use the Faceted Search Box to the left of the results to narrow your search.
You can also limit your search by Subject Area so that your search for "Mars" is limited to Science.
In the Advanced Search mode you can limit your search to one or more titles and one or more subject areas.
You can start your search with a Topic Page and let it direct you to recommended resources.
You can use a Search Gadget. This is useful when searching for a particular type of information - definitions, biography, images, pronunciations, quotations, etc.
Once you have exhausted Credo Reference's content you may expand your search to the Library Catalog, the library's databases, or the library's eBooks by using the drop down menu to the right of the search box.