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diff --git a/src/slalib/mxm.f b/src/slalib/mxm.f
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+      SUBROUTINE sla_MXM (A, B, C)
+*+
+*     - - - -
+*      M X M
+*     - - - -
+*
+*  Product of two 3x3 matrices:
+*      matrix C  =  matrix A  x  matrix B
+*
+*  (single precision)
+*
+*  Given:
+*      A      real(3,3)        matrix
+*      B      real(3,3)        matrix
+*
+*  Returned:
+*      C      real(3,3)        matrix result
+*
+*  To comply with the ANSI Fortran 77 standard, A, B and C must
+*  be different arrays.  However, the routine is coded so as to
+*  work properly on the VAX and many other systems even if this
+*  rule is violated.
+*
+*  P.T.Wallace   Starlink   5 April 1990
+*
+*  Copyright (C) 1995 Rutherford Appleton Laboratory
+*-
+
+      IMPLICIT NONE
+
+      REAL A(3,3),B(3,3),C(3,3)
+
+      INTEGER I,J,K
+      REAL W,WM(3,3)
+
+
+*  Multiply into scratch matrix
+      DO I=1,3
+         DO J=1,3
+            W=0.0
+            DO K=1,3
+               W=W+A(I,K)*B(K,J)
+            END DO
+            WM(I,J)=W
+         END DO
+      END DO
+
+*  Return the result
+      DO J=1,3
+         DO I=1,3
+            C(I,J)=WM(I,J)
+         END DO
+      END DO
+
+      END