Local derivation on triangular subalgebras of hyperfinite von Neumann algebras

It is proved that every σ - weakly continuous local derivation from triangular subalgebra A of hyperfinite von Neumann algebraB into A (or B) is a derivation. Morevoer, if A is also a σ-Dirichlet subalgebra, each local derivation from A into A is an inner derivation.