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      SUBROUTINE slETRM (EP, EV)

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      E T R M
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  Compute the E-terms (elliptic component of annual aberration)
  vector (double precision)

  Given:
     EP      dp      Besselian epoch

  Returned:
     EV      dp(3)   E-terms as (dx,dy,dz)

  Note the use of the J2000 aberration constant (20.49552 arcsec).
  This is a reflection of the fact that the E-terms embodied in
  existing star catalogues were computed from a variety of
  aberration constants.  Rather than adopting one of the old
  constants the latest value is used here.

  References:
     1  Smith, C.A. et al., 1989.  Astr.J. 97, 265.
     2  Yallop, B.D. et al., 1989.  Astr.J. 97, 274.

  P.T.Wallace   Starlink   23 August 1996

  Copyright (C) 1996 Rutherford Appleton Laboratory
  Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.

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