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Here are a few useful commands.
1) Search keywords in the Title of the web page.
allintitle: "douglas fir"
2) Search keywords in a specific web site or domain.
"douglas fir" site:.gc.ca
3) Search keywords and limit to a specific file format.
"douglas fir" filetype:pdf
The evolutionary biologist and author Richard Dawkins planted a Douglas Fir when he learned that his friend Douglas Adams, famous for writing the "Hitchhiker's Guide to the Galaxy" had died.
Source: Dawkins, R. (2001). Lament for Douglas Adams. Retrieved from: https://www.theguardian.com/uk/2001/may/14/books.booksnews