To limit your search to authoritative (trusted) sites:
Specify a preferred domain (.edu, .gov or .org) by adding site:.domain to your search.
"renal cell carcinoma" site:.gov
Be sure to include NO spaces between site: and the domain.
Use quotation marks:
For natural phrases (compound terms), such as traumatic brain injury, be sure to use quotation marks.
Example: "traumatic brain injury"