A REAL MATRIX R WITH NONNEGATIVE ENTRIES IS CALLED ROW SUB STOCHASTIC IF EACH ROW SUM ISAT MOST 1. FOR X, Y Î RN, WE SAY THAT X IS ROW SUB STOCHASTIC UPPER Triangular MAJORIZED BY Y (WRITE AS X≺SUT Y) IF THERE EXISTS A ROW SUB STOCHASTIC UPPER Triangular MATRIX R SUCH THAT X=RY. IN THIS PAPER, THE STRUCTURE OF ALL LINEAR functions T: R3 → R3, PRESERVING (STRONGLY PRESERVING)≺SUT ARE CHARACTERIZED.