 Complete the following phrase:  Some of Filittis biographical work was dedicated to the 16th-century Wallachian hero Michael the Brave. In 1931, he published an investigation of Michaels early career as titular Ban of Oltenia. A year later, he detailed Michaels introduction of serfdom in Wallachia: Despre legătura lui Mihai Viteazul On Bondage under Michael the Brave. Between these, the academic review Analele Economice și Statistice, Vol. XIV, reissued the 1857 count of emancipated Romani slaves, annotated by Filitti. In 1932, returning to the history of Oltenian Bans, he gave an account on the Craiovești family history, taken up by Arhivele Olteniei journal. His ongoing research into social issues of the early 19th century produced another book, Frământări politice și sociale în Principatele române de la 1821 la 1828 Political and Social Turmoil in the Romanian Principalities from 1821 to 1828, Cartea Românească, 1932. It has been described as a non-partisan analysis of the 