Tetrabiblos
... that Ptolemy's Tetrabiblos, a 2nd-century astrology book, is still considered a basic text in Western astrology?
... that <a href="./Ptolemy" id="mwC7k" rel="mw:WikiLink" title="Ptolemy">Ptolemy</a>'s <i id="mwC7o"><b id="mwC7s"><a href="./Tetrabiblos" id="mwC7w" rel="mw:WikiLink" title="Tetrabiblos">Tetrabiblos</a></b></i>, a 2nd-century astrology book, is still considered a basic text in <a href="./Western_astrology" id="mwC70" rel="mw:WikiLink" title="Western astrology">Western astrology</a>?