1. P. Battinelli, A. Brandimarti, and R. Capuzzo-Dolcetta, Astron. Astrophys. Suppl. Ser. 104, 379 (1994).
2. J. Caplan and L. Deharveng, Astron. Astrophys. 155, 297 (1986).
3. J. A. Cardelli, G. C. Clayton, and J. S. Mathis, Astrophys. J. 345, 245 (1989).
4. R. Cid Fernandes, A. Mateus, L. Sodre, Jr., et al., Mon. Not. R. Astron. Soc. 358, 363 (2005).
5. Yu. N. Efremov, Sites of Star Formation in Galaxies (Nauka, Moscow, 1989) [in Russian].