research on the history of mail order printing

[profes2]

I am attempting to do a study on the direct marketing of printed products starting in the 1930s. I am wondering if anyone has information on the subject and if they would be interested in possibly doing an interview.

My family operated a mail order wedding invitation business for years, so I have some knowledge, but I would really like to expand this into other products such as business cards and forms.

If anyone has information they would like to share pleas let me know.