Merge pull request #1 from mikel-egana-aranguren/master

Some content and bib added
Commit done before pushing the changes done by Mikel
Merge branch 'master' of https://github.com/alejandroriglesias/PPIO_SWJ

Conflicts:
	PPIO_SWJ.log
	PPIO_SWJ.pdf
Introduction section modified. This section has to be modified and completed, this is a test to check some parameters.
Introduction section modified with provisional initial paragraph. Changes need to be done (addition of more content)