Responsa for Shevuot 94:3

Q. A lent money, on trust, to B who subsequently left for a distant country where he was robbed of all his possessions. Upon his return he settled with A for three halves (half-pounds, marks), and gave A a note of indebtedness in which no specific date of month or day, but the calendar year since the creation of the world appeared, and which contained a clause to the effect that A is to be believed without an oath should any litigation arise concerning this debt. After B's death his widow seized his property in payment of her ketubah, which property barely covered ten percent of her claim, without taking the usual oath required of a widow upon the collection of her ketubah. Ten years after the death of B's widow, A presented his note for collection and demanded the full amount from B's sons. The latter claimed that their father left them nothing, that they inherited valuables from their mother only, and that B had paid A part of the debt contained in the note. A single witness testified, and A himself finally admitted, that B had repaid one-sixth of the debt.
A. A controversy exists regarding the status of the property seized by a widow in payment of her ketubah, if the widow died before taking the required oath. Some are of the opinion that the entire property reverts to the husband's estate; while others hold that the part of such property which is valued at no more than half of the amount of the widow's ketubah remains part of the widow's estate, while anything above that amount reverts to the husband's estate. The latter opinion is accepted. Therefore, if B's sons take an oath that they inherited nothing from their father, they are free from any obligation to A. If, however, they are willing to repay their father's debt, they may demand that A take an oath as to the amount actually due him, since he has been proven to be untrustworthy.
SOURCES: Pr. 859.