Wikipedia
https://en.wikipedia.org/wiki/Newsletter
What are newsletters? Learn about the history and role of newsletters in reaching out to people.
Top Rank Blog
http://www.toprankblog.com/2014/02/print-newsletters-content-marketing-tactic/
Find out how print newsletters are useful as a form of content marketing
Content Marketing Institute
http://contentmarketinginstitute.com/2012/10/print-content-strategy/
7 Reasons you should consider print media as a form of marketing strategy!
American Dental Association
America’s advocate group for dental health
British Dental Association
Professional association and trade union for dentists in the UK