Logos is the authority we give to a statement based on Logic. Generally, scholarly papers are Logos driven. They appeal to reason. We all see this in advertising as well. If A+B=C and we have proven A and B then we generally agree that C is true. This allows the person who reads the article or paper to come up with his own conclusion of truth based on known facts and information. Of course this information is not always conclusive or true in the first place. If we have given you false initial data then the conclusion can be false. All data can be skewed. You must trust the source of the data, which requires a certain amount of Ethos. Relying on quotations, facts and equations are all forms of the logical argument or Logos.