R. Guy, *Unsolved problems in number theory*, 3rd edition, Springer, 2004.

In this book, on page 167-168, Problem C5, *Sums determining members of a set*, discusses a question Leo Moser asked: suppose $X\subset\mathbb{Z}$ is an $n$-element set and $A$ be set of all $k$-element **sums** of subsets of $X$. Is there any other $Y\neq X$ such that $Y\subset\mathbb{Z}$ such that its $k$-element sums are exactly $A$?

Only small cases were known: $k=2,3,4,5$ and any $n$.

>**Question.** What is the general status of this problem for $k>5$? Are there (non-cosmetic) equivalent formulations of the question?