1) Consider limiting to a .edu, .org, .gov.
Example: "great depression" tulare site:.edu in Google
Example: "athletic apparel" "labor issues" site:.org in Google
2) Consider searching for you topic with archive, collection, digital collection, library, special collection, transcript, oral history etc.
Example: "naval technology" library
Example: "great depression" california "digital collection"
3) Consider using Google Advanced Search
4) Topic internationally focused? Consider searching in another country's Google domain