1. Frisk, U. O.: 1991, in Y. Kondo, ed(s)., Observatories in Earth Orbit and Beyond, Kluwer Academic Publishers, 223
2. Gautier, T.N., Boulanger, F., Pérault, M., and Puget, J.L.: 1992, AJ, 103, in press.
3. Hawarden, T. G., Bally, J. and Thronson, H. A.: 1992, in preparation,
4. Hawarden, T. G., Cummings, R., Telesco, C. M. and Thronson, H. A.: 1992, Space Science Reviews, this volume
5. Helou, G. and Beichman, C.: 1991, in EDITOR, ed(s)., From Ground-based to Space Borne Sub-Millimeter Astronomy, 29th Liege International Astrophysical Colloquium,