A friend showed me a paper that literally copied two pages of another paper, without any reference. This clearly is a fraud. He tried to inform the authors of the original paper. Is there any other way to deal with this situation?
I think the editor should not be the first contacting person. Because it will be a rude act. Even there is a possibility that you misunderstood the whole thing, and authors should ask for an opinion and explanation. Therefore, first of all, I will advise you to notify the authors and ask an explanation by sending an email. If he/she do not response your email or decline your claim, then send another email to the boss of the author (or the organizational head), if authors have an affiliation. If nothing happens, then contact the editor of the journal. In the email, you need to specify (page number, figure, methodology or idea) that can be considered as plagiarism.