Gitin9: 4
שְׁלשָׁה גִטִּין פְּסוּלִין; וְאִם נִשֵּׂאת — הַוָּלָד כָּשֵׁר: כָּתַב בִּכְתַב יָדוֹ, וְאֵין עָלָיו עֵדִים; יֵשׁ עָלָיו עֵדִים, וְאֵין בּוֹ זְמַן; יֶשׁ בּוֹ זְמַן, וְאֵין בּוֹ אֶלָּא עֵד אֶחָד. הֲרֵי אֵלּוּ שְׁלשָׁה גִטִּין פְּסוּלִין; וְאִם נִשֵּׂאת — הַוָּלָד כָּשֵׁר. רַבִּי אֶלְעָזָר אוֹמֵר: אַף עַל פִּי שֶׁאֵין עָלָיו עֵדִים, אֶלָּא שֶׁנְּתָנוֹ לָהּ בִּפְנֵי עֵדִים — כָּשֵׁר, וְגוֹבֶה מִנְּכָסִים מְשֻׁעְבָּדִים, שֶׁאֵין הָעֵדִים חוֹתְמִין עַל הַגֵּט אֶלָּא מִפְּנֵי תִקּוּן הָעוֹלָם.
Three gittin are void; but if she married, the offspring is legitimate: [if] he wrote [it] with his handwriting, but there are no witnesses on it; [if] there are witnesses on it, but it has no date; [if] it has a date, but it has only one witness. These three gittin are void; but if she married, the offspring is legitimate. R' Elazar says: Although there are no witnesses on it, but he gave it to her in the presence of witnesses, it is valid, and one collects from mortgaged properties, because witnesses sign on a document only for the sake of the general good.
Gitin9: 5
שְׁנַיִם שֶׁשָּׁלְחוּ שְׁנֵי גִטִּין שָׁוִין, וְנִתְעָרְבוּ — נוֹתֵן שְׁנֵיהֶם לָזוֹ וּשְׁנֵיהֶם לָזוֹ; לְפִיכָךְ, אָבַד אֶחָד מֵהֶן — הֲרֵי הַשֵּׁנִי בָטֵל.  חֲמִשָּׁה שֶׁכָּתְבוּ כְלָל בְּתוֹךְ הַגֵּט: ,,אִישׁ פְּלוֹנִי מְגָרֵשׁ פְּלוֹנִית, וּפְלוֹנִי פְּלוֹנִית”, וְהָעֵדִים מִלְּמַטָּה — כֻּלָּן כְּשֵׁרִין, וְיִנָּתֵן לְכָל אַחַת וְאֶחָת. הָיָה כָתוּב טֹפֶס לְכָל אַחַת וְאַחַת, וְהָעֵדִים מִלְּמַטָּה — אֶת שֶׁהָעֵדִים נִקְרִין עִמּוֹ כָּשֵׁר.
[If] two [men] sent two identical gittin, and they became mixed up, he gives both of them to this one and both of them to this one; therefore, [if] he lost one of them, the second is void.  [If] five wrote [as a] group in a get: “So-and-so is divorcing So-and-so, and So-and-so [is divorc-ing] So-and-so,” and the witnesses are below, they are all valid, and it shall be given to each one. [If] the text was written for each one, and the witnesses are below, that with which the witnesses are read is valid.