ABSTRACT
In this paper we are concerned with the characterization of real interpolation spaces (DA,E)α,∞ (Lions-Peetre, 19641 and (DA E)α (Da Prato-Grisvard, 1979), where A is an elliptic differential operator of order 2m, with general boundary conditions, and E is the Banach space of continuous functions on a bounded open set Ω ⊂ IRn; following Grisvard (1969), we denote such spaces by DA(θ,∞) and DA(θ), respectively, where θ = 1 - α.
