Fix some typos, style

[tkphd]

"Echebarria" was misspelled in the text. While editing the $\TeX$, I took the liberty of patching a few grammatical typos and re-formatted the list of variables using the symbols as item bullets. Also, using $\vec{j}$ (\vec{j}) is not as pretty as $\vec{\jmath}$ (\vec{\jmath}).

[david-montiel-t]

Looks good. Thank you, Trevor.