Complex sentence: In 1973, he entered the Law Department at Hitotsubashi University, and in 1980 completed his doctorate (Ph.D) in Law, writing his doctoral thesis on the diplomatic relations between France and Japan from 1914 to 1925.
Split into simpler sentences: In 1973, he entered the Law Department at Hitotsubashi University. In 1980, Polak wrote his doctoral thesis on the diplomatic relations between France and Japan from 1914 to 1925.