Ex.2

 Ex.2 https://drive.google.com/file/d/1r4CQ9PDfDF4uTU2nFE7Fvw1wjXaJOIC_/view?usp=sharing
 Ex.3 https://upcommons.upc.edu/bitstream/handle/2099.1/23420/ANTONI.CASTELLS_MASTER.THESIS.pdf?sequence=1&isAllowed=y