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+.help rverot Jun99 "Slalib Package"
+.nf
+
+      REAL FUNCTION slRVER (PHI, RA, DA, ST)
+
+     - - - - - - -
+      R V E R
+     - - - - - - -
+
+  Velocity component in a given direction due to Earth rotation
+  (single precision)
+
+  Given:
+     PHI     real    latitude of observing station (geodetic)
+     RA,DA   real    apparent RA,DEC
+     ST      real    local apparent sidereal time
+
+  PHI, RA, DEC and ST are all in radians.
+
+  Result:
+     Component of Earth rotation in direction RA,DA (km/s)
+
+  Sign convention:
+     The result is +ve when the observatory is receding from the
+     given point on the sky.
+
+  Accuracy:
+     The simple algorithm used assumes a spherical Earth, of
+     a radius chosen to give results accurate to about 0.0005 km/s
+     for observing stations at typical latitudes and heights.  For
+     applications requiring greater precision, use the routine
+     slPVOB.
+
+  P.T.Wallace   Starlink   20 July 1994
+
+  Copyright (C) 1995 Rutherford Appleton Laboratory
+  Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
+
+.fi
+.endhelp