Rules:

Only words from 2 to 200 characters are allowed.
Spaces are used as separators.
Quotes can be used to search on all the words between the quotes.
Boolean operators can also be used ("AND OR and NOT" or "+|-") for complexe searches.
Example: "constitution AND européenne" will find all the pages with these 2 words.
Example : "constitution OR européenne" will find all the pages with at least one of these words.
Example : "constitution NOT européenne" will find all the pages with only the first word and not the second one.