====== Capitolo 3: origine delle figure ======

  * Fig. 3.1 Castellani V. 1985, "Astrofisica Stellare,Zanichelli
  * Fig. 3.2 Clayton D.D. 1983, "Principles of  Stellar Evolution and Nucleosynthesis", McGraw-Hill
  * Fig. 3.3 Clayton D.D. 1983, "Principles of Stellar Evolution and Nucleosynthesis", McGraw-Hill
  * Fig. 3.4 Hayashi C., Hoshi R., Sugimoto D. 1962, Progr. Theor. Physics, Suppl 22.
  * Fig. 3.5 Ezer D., Cameron A.G.W. 1963, Icarus 1, 422.
  * Fig. 3.6 Castellani V. 1985, "Astrofisica Stellare, Zanichelli
  * Fig. 3.12 Clayton D.D. 1983, "Principles of Stellar Evolution and Nucleosynthesis", McGraw-Hill
  * Fig. 3.14 Clayton D.D. 1983, "Principles of Stellar Evolution and Nucleosynthesis", McGraw-Hill