filename	IN:	Name of the file
	ref	IN:	Reference number for next DFR8getimage

	Purpose	Specifies the reference number of the image to be read when DFR8getimage is next called.
	Return value	Returns SUCCEED (or 0) if successful and FAIL (or -1) otherwise.
	Description	DFR8readref is usually used in conjunction with DFANlablist, which returns a list of labels for a given tag together with their reference numbers. It provides, in a sense, a random access to images. There is no guarantee that reference numbers appear in sequence in an HDF file; therefore, it is not safe to assume that a reference number is the index of an image.

	FORTRAN	integer function d8rref(filename, ref)
		character*(*) filename
		integer ref