Relaxation method to solve the differential equation

Reference:

"The second method for numerical solution of BVPs is known as finite differences, relaxation, or -in the specific case of stellar structures- the Henyey method".

! IMPORTANT!

http://dipastro.pd.astro.it/chiosi/Lezioni/LAUREA_TRIENNALE/ASTROFISICA_II_MOD_B/LEZIONE_XIV/Binder_XIV.pdf

Lectures on Numerical Mathematics 

chapter 10 Relaxation Methods 

HENYEY RELAXATION METHOD REVISITED: AN APPLICATION TO PROBLEMS INVOLVING

CRITICAL POINTS

FUNDAMENTALS OF ENGINEERING NUMERICAL ANALYSIS