“…The concept of differential subalgebras of order θ was introduced in [7,26,32] for θ = 1 and [12,20,36] for θ ∈ (0, 1). We also refer the reader to [3,15,19,20,21,25,33,34,41,42,43,45] for various differential subalgebras of infinite matrices, convolution operators, and integral operators with certain off-diagonal decay.…”