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When I use the dictionary such as Wilhelm Gesenius (Hebrew and Chaldee Lexicon) and Marcus Jastrow (Dictionary of Targumim, Talmud and Midrashic Literature) I have difficulty in understanding the differences between the Syriac and Aramaic. Is there a clear-cut between these languages or are they approximately the same thing?

I am interested especially in Christian but also in Jewish, Syriac and Zoroastrian works and authors. I know only one publication on this matter by David M. Olster: Roman Defeat, Christian Response, and the Literary Construction of the Jew, University of Pennsylvania Press, 1994. I thank you in advance for any suggestions you may have.