"Phrase Searching" means searching for two or more words as an exact phrase. This allows Neo to find documents containing a particular phrase e.g. “air pollution” or “biofuel energy”.
Neo can try Snowballing: assuming he finds at least one relevant journal article he can use as a basis for future searches, for example:
Neo can look at the list of references at the end of the article to see what related work the author has cited.