Analytical solution for the Shock Tube
 

Hi there,
I am trying to understand the analytical solution of the Shock tube, an for that I downloaded a Matlab code with the attached PDF. There are only three equations in the PDF, and I was wondering if any one can suggest a reference to understand them.
also, the complete code and PDF can be found herehttp://sitemaker.umich.edu/anand/fil...shock-tube.pdf
Thank you in advance.