clarify a definition, fix 2 typos
typo in basic.tex
Typos in 5.2 and 10.5
Deleted an obsolete sentence
Merge pull request #682 from jledent/obsolete

Deleted an obsolete sentence
changed x to p
Merge pull request #680 from jledent/basics

typo in basic.tex
Merge pull request #681 from jledent/typos

Typos in 5.2 and 10.5