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diff --git a/src/slalib/xy2xy.f b/src/slalib/xy2xy.f
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+      SUBROUTINE sla_XY2XY (X1,Y1,COEFFS,X2,Y2)
+*+
+*     - - - - - -
+*      X Y 2 X Y
+*     - - - - - -
+*
+*  Transform one [X,Y] into another using a linear model of the type
+*  produced by the sla_FITXY routine.
+*
+*  Given:
+*     X1       d        x-coordinate
+*     Y1       d        y-coordinate
+*     COEFFS  d(6)      transformation coefficients (see note)
+*
+*  Returned:
+*     X2       d        x-coordinate
+*     Y2       d        y-coordinate
+*
+*  The model relates two sets of [X,Y] coordinates as follows.
+*  Naming the elements of COEFFS:
+*
+*     COEFFS(1) = A
+*     COEFFS(2) = B
+*     COEFFS(3) = C
+*     COEFFS(4) = D
+*     COEFFS(5) = E
+*     COEFFS(6) = F
+*
+*  the present routine performs the transformation:
+*
+*     X2 = A + B*X1 + C*Y1
+*     Y2 = D + E*X1 + F*Y1
+*
+*  See also sla_FITXY, sla_PXY, sla_INVF, sla_DCMPF
+*
+*  P.T.Wallace   Starlink   5 December 1994
+*
+*  Copyright (C) 1995 Rutherford Appleton Laboratory
+*-
+
+      IMPLICIT NONE
+
+      DOUBLE PRECISION X1,Y1,COEFFS(6),X2,Y2
+
+
+      X2=COEFFS(1)+COEFFS(2)*X1+COEFFS(3)*Y1
+      Y2=COEFFS(4)+COEFFS(5)*X1+COEFFS(6)*Y1
+
+      END