The search would have first looked for the set of texts that contains both the words frontier And pioneer . Next it would have looked for the texts that contain the word Indian . Then it would combine those two sets of results and eliminate the duplicates to produce the final result. This means that you would have a whole set of texts that contained the word Indian , but not frontier And pioneer . The search operates first on the smallest innermost bracket, second on the next largest bracket and the results of the first bracket, and third on the outermost term and the results of the second bracket.
Proximity Searches A proximity search looks for the co-occurrence of two or three search terms.
Finding instances where a term is either Followed By or Near another. Looking for places where words are Not Followed By or Not Near other words. For example, if you want to find texts in which the terms Mississippi River and steamboat appear relatively Near each other, search for those terms within 40 characters of one another. To find those terms only when one follows another, select the Followed By proximity operator. If you want to find all instances where a term is not followed by another closely associated term, you may use the Not Followed By or Not Near operators.