Minimal reducible bounds for the class of k-degenerate graphs

Let (La,⊆) be the lattice of hereditary and additive properties of graphs. A reducible property R∈La is called minimal reducible bound for a property P∈La if in the interval (P,R) of the lattice La, there are only irreducible properties. We prove that the set B(Dk)={Dp∘Dq: k=p+q+1} is the covering set of minimal reducible bounds for the class Dk of all k-degenerate graphs.