Reference for Sukkah 3:6
עָלְתָה חֲזָזִית עַל רֻבּוֹ, נִטְּלָה פִטְמָתוֹ, נִקְלַף, נִסְדַּק, נִקַּב וְחָסַר כָּל שֶׁהוּא, פָּסוּל. עָלְתָה חֲזָזִית עַל מִעוּטוֹ, נִטַּל עֻקְצוֹ, נִקַּב וְלֹא חָסַר כָּל שֶׁהוּא, כָּשֵׁר. אֶתְרוֹג הַכּוּשִׁי, פָּסוּל. וְהַיָרוֹק כְּכַרְתִי, רַבִּי מֵאִיר מַכְשִׁיר, וְרַבִּי יְהוּדָה פּוֹסֵל:
If most of it (the ethrog) were covered with lichen (it is pasul) [It is in one place that "most of it" is required (to render it "pasul"); but in two or three places, even (if lichen covered) the lesser part of it, it is pasul. And on its pitma (its upper protuberance, as in "the pitma of a pomegranate"), even any amount (so covered) renders it pasul, it being more conspicuous there than in other places.] If its pitma were removed, if it were peeled, if it were split, if it were punctured and something of it were missing, it is pasul. [("if it were peeled":) Only if most of it were peeled; but if part of it, it is kasher. Others say the opposite, viz.: If part of it were peeled, it is pasul; for then it looks "spotted." But if all of it were peeled, it is kasher. "peeled" here does not mean that the skin was removed so that the white could be seen; for in that instance it would be chasser ("lacking") and pasul; but that a thin layer was removed and its appearance is green as before. ("punctured":) If it were punctured through and through, even a very slight puncture, it is pasul. And if it did not go through and nothing were lost, as when he stuck a thick peg into it — if the hole were as wide as an issar (a Roman coin), it is pasul; if less than that, it is kasher. And this is the intent of "if it were punctured but lacked nothing" below, i.e., not punctured through and through, and not as wide as an issar.] If its lesser part were covered with lichen, if its uketz ("tail," peduncle) were removed, or if it were punctured but lacked nothing, it is kasher. An Ethiopian ethrog [one that grows here (in Eretz Yisrael), but is black] is pasul. [But such an ethrog growing in Ethiopia is the norm and is kasher. A leek-green ethrog — R. Meir rules it kasher; R. Yehudah rules it pasul. [All of these are pasul only on the first festival, but on the second and the intervening days, everything is kasher.]