Research on Crack, Hurt, Pain

https://www.mylifestages.org/asktheexpert/QuestionAnswer.page?questionid=1539

http://wiki.answers.com/Q/Does_cracking_your_shoulders_or_neck_cause_any_permanent_damage

http://www.dailymail.co.uk/health/article-2156179/Letting-chiropractor-crack-neck-ease-pain-trigger-stroke.html

http://www.wisegeek.org/what-is-a-soft-tissue-injury-in-a-car-accident.htm