Check out this legally free ebook:

  • Dogmatic theology II. The Divine Trinity, a dogmatic treatise, by Pohle, Joseph, translated by Arthur Preuss. St. Louis: Herder, 1916. With Imprimatur. Available in multiple formats at Internet archive (Digitizing sponsor: MSN, Book contributor: Kelly – University of Toronto) as of February 12, 2012. The 1912 edition is also available at Internet Archive and Open Library (Digitizing sponsor: Google, Book from the collections of: New York Public Library)