Complex sentence: Morgenthau completed his doctoral dissertation in Germany in the late 1920s which was published in 1929 as his first book entitled, "The International Administration of Justice, Its Essence and Its Limits".
Split into simpler sentences: Morgenthau completed his doctoral dissertation in Germany in the late 1920s. It was published in 1929 as his first book, "The International Administration of Justice, Its Essence and Its Limits".