[DoH]= Dong, Y.S., Hu, J.Y. 1991, Chin. A&A, 15, 275 (1991ChA&A..15..275D)
  [OuE]= Oudmaijer, R.D., v.d. Veen, W.E.C.J., Waters, L.B.F.M., Trams, N.R.,
          Waelkens, C., Engelsman, E., 1992; A&AS 96, 625 (1992A&AS...96..625O)