Related for Kiddushin 4:3
כָּל הָאֲסוּרִים לָבֹא בַקָּהָל, מֻתָּרִים לָבֹא זֶה בָזֶה. רַבִּי יְהוּדָה אוֹסֵר. רַבִּי אֱלִיעֶזֶר אוֹמֵר, וַדָּאָן בְּוַדָּאָן, מֻתָּר. וַדָּאָן בִּסְפֵקָן, (וּסְפֵקָן בְּוַדָּאָן), וּסְפֵקָן בִּסְפֵקָן, אָסוּר. וְאֵלּוּ הֵן הַסְּפֵקוֹת, שְׁתוּקִי, אֲסוּפִי וְכוּתִי:
All who are forbidden to enter the congregation are permitted to intermarry with each other. [Even though it was already taught that mamzerim, Nethinim, etc. are permitted to intermarry, we are being apprised here that one such as a Moavite or Ammonite proselyte may marry a mamzer, a shetuki, or an asufi. R. Yehudah forbids. [The gemara explains: Even R. Yehudah, who forbids a mamzereth to a proselyte, forbids it only to a proselyte from other gentile nations, who are permitted to enter the congregation (R. Yehudah holding that the congregation of proselytes is called a "congregation"), but he concedes that a Moavite or Ammonite proselyte, who is forbidden to enter the congregation, is permitted to marry a mamzereth.] R. Eliezer says: A confirmed one with a confirmed one [such as a mamzer with a Nathin] is permitted. A confirmed one with a doubtful one [a mamzer or a Nathin with a shetuki or an asufi] and a doubtful one with a doubtful one [a male shetuki with a female shetuki, or a male asufi with a female asufi, or an asufi with a shetuki] are forbidden [even though both are doubtful; for one might be kasher and the other, pasul. The halachah is in accordance with R. Eliezer.] These are the doubtful ones: shetuki, asufi, and Cuthi. [Cuthites are "doubtful," because they are not versed in the laws of gittin and betrothal. And today they are considered confirmed gentiles in all respects.]