premise: The subject of Jewish gangsterism has been well mined in recent years by both historians and  Albert Fried's The Rise and Fall of the Jewish Gangster in America and Jenna Weissman Joselit's Our  Jewish Crime and the New York Jewish Community--1900-1940 are two recent additions to the nonfiction literature, and films such as Once Upon a Time in America and Bugsy feature Jewish criminality.
hypothesis: Both Albert Fried and Jenna Weissmann Joselit wrote about Jewish gangsterism, but everyday many researchers study it for their thesis.