Reference for Sukkah 12:9

רבנן סברי יש אם למסורת (ויקרא כג, מב) בסכת בסכת בסכות הרי כאן ארבע

‘The rabbis hold that the traditional Scriptural text is authoritative’, and the word Sukkoth occurs twice defectively and once with the full spelling, making four references. Deduct one for the law itself, and three remain;

Jastrow