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diff --git a/src/slalib/imxv.f b/src/slalib/imxv.f
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+      SUBROUTINE sla_IMXV (RM, VA, VB)
+*+
+*     - - - - -
+*      I M X V
+*     - - - - -
+*
+*  Performs the 3-D backward unitary transformation:
+*
+*     vector VB = (inverse of matrix RM) * vector VA
+*
+*  (single precision)
+*
+*  (n.b.  the matrix must be unitary, as this routine assumes that
+*   the inverse and transpose are identical)
+*
+*  Given:
+*     RM       real(3,3)    matrix
+*     VA       real(3)      vector
+*
+*  Returned:
+*     VB       real(3)      result vector
+*
+*  P.T.Wallace   Starlink   November 1984
+*
+*  Copyright (C) 1995 Rutherford Appleton Laboratory
+*-
+
+      IMPLICIT NONE
+
+      REAL RM(3,3),VA(3),VB(3)
+
+      INTEGER I,J
+      REAL W,VW(3)
+
+
+
+*  Inverse of matrix RM * vector VA -> vector VW
+      DO J=1,3
+         W=0.0
+         DO I=1,3
+            W=W+RM(I,J)*VA(I)
+         END DO
+         VW(J)=W
+      END DO
+
+*  Vector VW -> vector VB
+      DO J=1,3
+         VB(J)=VW(J)
+      END DO
+
+      END