1. P. E. Seiden, L. Schulman, and J. V. Feitzinger, Astrophys. J.,253, 91 (1982).
2. G. Bodifee and C. de Loore, Astron. Astrophys.,142, 297 (1985).
3. C. Lada, L. Blitz, and B. G. Elmegreen, in: Protostars and Planets (ed. T. Gehrels), University of Arizona Press (1979).
4. B. G. Elmegreen, in: Star Forming Region, Dordrecht (1987).
5. P. E. Seiden and H. Gerola, Astrophys. J.,233, 56 (1979).