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diff --git a/src/slalib/pcd.f b/src/slalib/pcd.f
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+      SUBROUTINE sla_PCD (DISCO,X,Y)
+*+
+*     - - - -
+*      P C D
+*     - - - -
+*
+*  Apply pincushion/barrel distortion to a tangent-plane [x,y].
+*
+*  Given:
+*     DISCO    d      pincushion/barrel distortion coefficient
+*     X,Y      d      tangent-plane coordinates
+*
+*  Returned:
+*     X,Y      d      distorted coordinates
+*
+*  Notes:
+*
+*  1)  The distortion is of the form RP = R*(1 + C*R**2), where R is
+*      the radial distance from the tangent point, C is the DISCO
+*      argument, and RP is the radial distance in the presence of
+*      the distortion.
+*
+*  2)  For pincushion distortion, C is +ve;  for barrel distortion,
+*      C is -ve.
+*
+*  3)  For X,Y in units of one projection radius (in the case of
+*      a photographic plate, the focal length), the following
+*      DISCO values apply:
+*
+*          Geometry          DISCO
+*
+*          astrograph         0.0
+*          Schmidt           -0.3333
+*          AAT PF doublet  +147.069
+*          AAT PF triplet  +178.585
+*          AAT f/8          +21.20
+*          JKT f/8          +13.32
+*
+*  4)  There is a companion routine, sla_UNPCD, which performs
+*      an approximately inverse operation.
+*
+*  P.T.Wallace   Starlink   31 December 1992
+*
+*  Copyright (C) 1995 Rutherford Appleton Laboratory
+*-
+
+      IMPLICIT NONE
+
+      DOUBLE PRECISION DISCO,X,Y
+
+      DOUBLE PRECISION F
+
+
+
+      F=1D0+DISCO*(X*X+Y*Y)
+      X=X*F
+      Y=Y*F
+
+      END