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      SUBROUTINE slVN (V, UV, VM)

     - - -
      V N
     - - -

  Normalizes a 3-vector also giving the modulus (single precision)

  Given:
     V       real(3)      vector

  Returned:
     UV      real(3)      unit vector in direction of V
     VM      real         modulus of V

  If the modulus of V is zero, UV is set to zero as well

  P.T.Wallace   Starlink   23 November 1995

  Copyright (C) 1995 Rutherford Appleton Laboratory
  Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.

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