Search string may contain the logical operators AND and OR and the operands () and "".
AND searches for both words or phrases, while OR searches for one or the other.
If the search string uses AND and OR at the same time, the AND operation takes priority,
unless you enclose the OR operation in parentheses, as in (A or B) and C. To find
an exact phrase, such as "gambia population", enclose the phrase in quotes.