Beraisa: If two people were holding onto a loan document, one (i.e. the lender) claiming that it is his and it fell from him and the other (i.e. the borrower) claiming that he had already paid off the loan...

Rebbi: You must validate the document through its signatures (otherwise the debt cannot be collected).

Rabban Gamliel: You should divide the money.

R. Elazar: The money is awarded to the one who is holding onto the place of the witnesses in the document.

Rav Chisda: In order to say this, you must be following the opinion of Rabban Shimon ben Gamliel (but according to Rebbi, everything follows the validation of the document).

If one said that half is his and the other one said that 1/3rd is his, the first one swears that he has no less than 1/4 of it and the second one swears that he has no less than 1/6th.

The rule is that one only swears on half of that which he claimed.