Reference for Yevamot 13:11
גְּדוֹלָה וּקְטַנָּה, בָּא יָבָם עַל הַגְּדוֹלָה, וְחָזַר וּבָא עַל הַקְּטַנָּה, אוֹ שֶׁבָּא אָחִיו עַל הַקְּטַנָּה, לֹא פָסַל אֶת הַגְּדוֹלָה. בָּא יָבָם עַל הַקְּטַנָּה, וְחָזַר וּבָא עַל הַגְּדוֹלָה, אוֹ שֶׁבָּא אָחִיו עַל הַגְּדוֹלָה, פָּסַל אֶת הַקְּטַנָּה. רַבִּי אֶלְעָזָר אוֹמֵר, מְלַמְּדִין הַקְּטַנָּה שֶׁתְּמָאֵן בּוֹ:
If a yavam-minor cohabited with a yevamah-minor, they are to "grow up" with each other [and he cannot divorce her until he comes of age, for the get of a minor is not a get.] If he cohabited with a yevamah-adult, she is to wait until he comes of age. If the yevamah said in the midst of thirty days [after the yavam took her]: I was not cohabited with, [and the yavam says: I did cohabit with you, and a get suffices for you], he is compelled to give her chalitzah. [For she is believed. For until thirty days one can restrain himself and not cohabit.] After thirty days, he is requested to give her chalitzah. [After thirty days he is believed; for a man cannot restrain himself from cohabiting for more than thirty days. However, she is not thereby permitted, having rendered herself forbidden and in need of chalitzah, so that he is requested to give her chalitzah. But he is not compelled, for he says that he did cohabit with her. As to his being compelled to give chalitzah in the midst of thirty days and being requested to give chalitzah after thirty days, and not being compelled and requested to take her in yibum — the gemara posits this to be an instance where she presents a get; for having given a get to his linked one, she is rendered unfit to him. But she still requires chalitzah to permit her to others. And if (after thirty days) she says: I was cohabited with, and he says: I did not cohabit with her, we pay no heed to his word, and she does not require chalitzah.] And when he concedes (that he did not cohabit with her), even after twelve months, he is compelled to give her chalitzah.