Reference for Eruvin 109:10

היתה עשויה כמין קשת או כמין גאם רואין אותה כאילו היא מלאה בתים וחצירות ומודד ממנה ולהלן אלפים אמה אמר רב הונא עיר העשויה כקשת אם יש בין שני ראשיה פחות מארבעת אלפים אמה מודדין לה מן היתר ואם לאו מודדין לה מן הקשת

Now that you said that law applied to one house, was it also necessary to mention two houses? - The ruling was necessary in that case only where the two houses were respectively on two sides of the town. As it might have been presumed that we apply the law only where a projecting house was on one side but not when houses were projecting on two sides, we were informed [that the law is applied to the latter case also].' If the town was shaped like a bow or like a gamma, it is to be regarded as if it had been full of houses an courtyards, and the two thousand cubits are measured from its imaginary boundaries'. R'Huna laid down: If a town is shaped like a bow, then, if the distance between its two ends<span class="x" onmousemove="('comment',' I.e., the side corresponding to the bow string.');">²⁶</span>

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