From Paris, Schwarzfeld continued his literary activity in behalf of his Romanian coreligionists, and he was co-editor of "Egalitatea" ("Equality"), the Bucharest-based Jewish periodical founded in Bucharest by his brother. He had an international career as an essayist and historian: in 1901, the "American Jewish Year Book" published his "The Jews of Rumania from the Earliest Time to the Present Day" and "The Situation of the Jews in Rumania Since the Berlin Treaty (1878)"; an essay on "The Jews of Moldavia at the Beginning of the Eighteenth Century" appeared in "The Jewish Quarterly Review", vol. xvi., and another entitled "Deux episodes de l'histoire des juifs roumains" in the "Revue des Études Juives", vol. xiii. His "Les juifs en Roumaine depuis le Traité de Berlin" ("The Jews of Romania since the Berlin Treaty") appeared under the pseudonym "Edmond Sincerus" (London, 1901).