  A finite graph with an assignment of non-negative integers to vertices gives
chip-firing games. Chip-firing games determine languages (sets of words) called
the record sets of legal games. Bj\"orner, Lov\'asz and Shor found several
properties that are satisfied by record sets. In this paper, we will find two
more properties of record sets. Under the assumption that the record set is
finite and the game fires only two vertices, these properties characterize the
record sets of graphs.
