def get_reference_position(filename):
    """
    Read a Vizier SED VOT file and parse the reference position.

    Parmaeters
    ----------
        filename : the name of a Vizier SED VOT file

    Returns
    -------
        ra0 : (float) the reference position RA in decimal degrees

        dec0 : (float) the reference position Dec in decimal degrees

        search_radius : (float) the search radius for the query in
                        arc-seconds

    """
    infile = open(filename)
    lines = infile.readlines()
    infile.close()
    try:
        for line in lines:
            line = line.strip('\n')
            if '<INFO ID="Target"' in line:
                values = line.split('"')
                str1 = values[-2]
                fields = str1.split(',')
                if '+' in fields[0]:
                    v1 = fields[0].split('+')
                    ra0 = float(v1[0])
                    dec0 = float(v1[1])
                else:
                    v1 = fields[0].split('-')
                    ra0 = float(v1[0])
                    dec0 = -1. * float(v1[1])
                search_radius = float(fields[1].replace('rs=', ''))
                return ra0, dec0, search_radius
        return None, None, None
    except:
        return None, None, None