Finding magazine articles, reports and academic studies that support your topic can bring enormous credibility to you and your book. Of course not. For instance, referring to a recent Wall Street Journal could add credibility. Quoting a study conducted at Duke or Stanford will certainly bring independent validation to your words. Research is traditionally contracted by the hour.
Every professional writer knows that all good writing is really only skillful rewriting.
Look, David Letterman's show is simply a rewrite of the old Ernie Kovak's show. All new rock music is simply a rewrite of 50's and 60's music. All encyclopedias . . . Your writer's job is to make your book easier to read and create more value than is in the other books on your subject. Let's say you take the facts from a document published by Medicare, or Vanguard.