Irish Immigration to Chicago published by the University of California Press is a credible source. It is credible because there are over 4,000 titles to choose from in all different subjects such as humanities, science, and social studies, etc. The UC Press publishes books and articles for academic purposes. The book Urban Revolt by Eric Hirsch was published by UC Press. Any article, or book published by Hirsch is credible because he has written many books for academic purposes, and is a professor in this area so he knows what he is talking about.