Evaluate the sources the author uses.In doing this,be certain that the sources are credible.For example,Einstein is a credible source if the author is writing about landmark achievements in physics.Also be certain that the sources are relevant.Einstein is not a relevant source when the subject is poetry.Finally,if the author is writing about a subject in its current state,be sure that the sources are current.For example,studies done by Einstein in the early 20th century may not be appropriate if the writer is discussing the current state of knowledge in physics.