Even a well designed search engine like Google only samples a small proportion of all that exists on the internet.
If the information on Google is limited, look for a search engine that specializes in your topic. Maybe you can find an expert's list of the best sites for your needs, or you might need to use a database that isn't free.
To break out of the Google box, you can try the library's subscription databases, ask a reference librarian for ideas, or check internet sites such as those below.
And don't forget, sometimes what you seek might be found in the library - in a book.