Some writers try to influence their readers by including the views of celebrities or experts in their argument. Although celebrities may not be well informed on a topic, some readers are convinced of a claim's truthfulness if they read that somebody famous endorses such a view. However, celebrity endorsements usually provide little solid evidence that can be used to prove or disprove a claim.

On the other hand, including opinions from scientists, researchers, and other experts is a valuable tactic that can provide necessary information that a reader needs to make an informed decision. The reader should be informed of the expert's qualifications, and the expert cited should have some relevance to the question at hand. For example, ufologists and doctors can give their opinion about whether physical marks on abductees' bodies or metal objects found under their skin are really signs...