Linear isometries of the domain D(δ2) of the square of a closed ∗-derivation δ

The domain D(δ2) of the square of a closed ∗-derivation δ in C(K) (K is a compact Hausdorff space) is a generalization of the space C(2)[0,1]. In this paper, we determine extreme points of and the structure of surjective linear isometries of D(δ2) with some graph norm.