1 O.. Vilhu, C.W. Ambruster, J.E. Neff, J.L. Linsky, A.. Brandenburg, I.V. Ilyin, and N.I. Shakovskaya, Astronomy and Astrophysics 222, (1989).
1 O.. Vilhu, J.-P.. Caillault, J.E. Neff, and J.. Heise, in (Springer Netherlands, Dordrecht, 1988), pp. 179–182.