1. Woolf, N. J., in Interstellar Dust and Related Topics (edit. by Greenberg, J. M., and van de Hulst, H. C.) (D. Reidel Co., 1973).
2. Chiao, R. Y., Feldman, M. J., and Parrish, P. T., in Interstellar Dust and Related Topics (edit. by Greenberg, J. M., and van de Hulst, H. C.) (D. Reidel Co., 1973).
3. Caroff, L. J., Petrosian, V., Salpeter, E. E., Wagoner, R. V., and Werner, M. W., Mon. Not. R. Astr. Soc., 164, 295 (1973).
4. Danielson, R. E., Woolf, N. J., and Gaustad, J. E., Astrophys. J., 141, 116 (1965).
5. Knacke, R. F., Cudaback, D. D., and Gaustad, J. E., Astrophys. J., 158, 151 (1969).