Wired Science compilation using Nicholas Longrich's skull reconstruction on right
We could spend all day today simply linking articles that are about, mention, or vaguely address Pentaceratops. There are not enough hours in the day to read all the papers I found within the first ten seconds of searching for articles to read. There are later discoveries of skulls that are described, "new" compilations of data on the dinosaur genus (from 1993), and even re-evaluations of the genus as a whole. If you can find a copy I recommend, as always, reading the original description by HF Osborn and CH Sternberg which is only 3 pages and was published by the American Museum of Natural History. I also recommend reading Longrich's paper announcing Titanoceratops ouranosfrom 2011. The majority agreement at the moment is that Titanoceratops is a junior synonym of Pentaceratops, and that is the key reason I would say it is important to read this paper.