      FUNCTION ERFC2(X)
C     ------------------
C     EVALUATION OF ERFC(X) FOR ABS(X) .LE. 4.0
C     ------------------
      DATA P0/2.13853322378E+01/, P1/1.72227577039E+00/,
     *     P2/3.16652890658E-01/
      DATA Q0/1.89522572415E+01/, Q1/7.84374570830E+00/
C     ------------------
      DATA R0/7.3738883116E+00/, R1/6.8650184849E+00/,
     *     R2/3.0317993362E+00/, R3/5.6316961891E-01/,
     *     R4/4.3187787405E-05/
      DATA S0/7.3739608908E+00/, S1/1.5184908190E+01/,
     *     S2/1.2795529509E+01/, S3/5.3542167949E+00/
C
      A = ABS(X)
      T = A*A
      IF (A .GE. 0.5) GO TO 10
          ERFC2 = 1.0 - X*((P2*T + P1)*T + P0)/((T + Q1)*T + Q0)
          RETURN
   10 W = ((((R4*A + R3)*A + R2)*A + R1)*A + R0)/
     *       ((((A + S3)*A + S2)*A + S1)*A + S0)
      ERFC2 = EXP(-T)*W
      IF (X .LT. 0.0) ERFC2 = 2.0 - ERFC2
      RETURN
      END
