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2,(HH) which follows easily from the midpoint and trapezoidal approximation to the middle term. Moreover, under the presence of continuity, equality occurs (in either side) only for linear functions. An updated account on (HH) are to be found in 2]. What about the case of functions of several variables? A recent paper by SS Dragomir 3](see also 2]) describes the case of balls in R3, by proving that f (a) 6