וְהַצָּפִ֥יר הַשָּׂעִ֖יר מֶ֣לֶךְ יָוָ֑ן וְהַקֶּ֤רֶן הַגְּדוֹלָה֙ אֲשֶׁ֣ר בֵּין־עֵינָ֔יו ה֖וּא הַמֶּ֥לֶךְ הָרִאשֽׁוֹן׃
And the rough he-goat is the king of Greece; and the great horn that is between his eyes is the first king.
Read halakhic rulings (Jewish law) on Daniel 8:21: and classical halakhic sources.