How to Express Agreement and Disagreement: So, Either and Neither.

http://learnenglishteens.britishcouncil.org/exams/speaking-exams/agreeing-and-disagreeing

http://www.shertonenglish.com/resources/es/miscelaneous-topics/agreement.php

http://esl.about.com/od/grammarintermediate/a/cm_sneither.htm

http://todayschool.es/blog/grammar/grammar-practice-auxiliary-verbs-so-do-i-neither-do-i-etc-3a/

http://www.usingenglish.com/quizzes/68.html

http://www.ecenglish.com/learnenglish/lessons/so-and-neither