Reference for Yevamot 4:13
אֵיזֶהוּ מַמְזֵר, כָּל שְׁאֵר בָּשָׂר שֶׁהוּא בְלֹא יָבֹא דִּבְרֵי רַבִּי עֲקִיבָא. שִׁמְעוֹן הַתִּימְנִי אוֹמֵר, כָּל שֶׁחַיָּבִין עָלָיו כָּרֵת בִּידֵי שָׁמַיִם. וַהֲלָכָה כִדְבָרָיו. רַבִּי יְהוֹשֻׁעַ אוֹמֵר, כָּל שֶׁחַיָּבִים עָלָיו מִיתַת בֵּית דִּין. אָמַר רַבִּי שִׁמְעוֹן בֶּן עַזַּאי, מָצָאתִי מְגִלַּת יֻחֲסִין בִּירוּשָׁלַיִם וְכָתוּב בָּהּ, אִישׁ פְּלוֹנִי מַמְזֵר מֵאֵשֶׁת אִישׁ, לְקַיֵּם דִּבְרֵי רַבִּי יְהוֹשֻׁעַ. אִשְׁתּוֹ שֶׁמֵּתָה, מֻתָּר בַּאֲחוֹתָהּ. גֵּרְשָׁהּ וָמֵתָה, מֻתָּר בַּאֲחוֹתָהּ. נִשֵּׂאת לְאַחֵר וָמֵתָה, מֻתָּר בַּאֲחוֹתָהּ. יְבִמְתּוֹ שֶׁמֵּתָה, מֻתָּר בַּאֲחוֹתָהּ. חָלַץ לָהּ וָמֵתָה, מֻתָּר בַּאֲחוֹתָהּ:
Which is a mamzer? (The child of) any kin with whom marriage is interdicted. These are the words of R. Akiva. Shimon Hatemani says: (The child of) all kin with whom marriage is interdicted by kareth at the hands of heaven, [but not (merely) by negative commandment]. And this is the halachah [i.e., that the child of a kareth-interdicted marriage is a mamzer (except the child of a niddah), but the child of a marriage interdicted by negative commandment (alone) is not a mamzer.] R. Yehoshua says: All kin with whom marriage is interdicted by judicial death penalty. R. Shimon b. Azzai said: I found a pedigree-scroll in Jerusalem, in which it was written: "Such and such is a mamzer from an adulterous union (in confirmation of the word of R. Yehoshua.) If one's wife died, he may marry her sister. If he divorced her and she died, he may marry her sister. If she married another and she died, he may marry her sister. If one's yevamah died, he may marry her sister. If he gave her chalitzah and she died, he may marry her sister.