Normal Derivative for Bounded Domains with General Boundary
Gong Guanglu, Qian Minping, Martin L. Silverstein · Transactions of the American Mathematical Society · 1988
Gong Guanglu, Qian Minping, Martin L. Silverstein, Normal Derivative for Bounded Domains with General Boundary, Transactions of the American Mathematical Society, Vol. 308, No. 2 (Aug., 1988), pp. 785-809