Sources:

http://www.dataservicesinc.com/newsletter/case-study-customer-reactivation-using postcards/

Past Customer Reactivation: 8 Tips to Get Those Clients Back

http://targetmarketingmag.com/article/3-ways-reactivate-lapsed-customer-direct-mail/

https://conversio.com/blog/reactivate-past-customners-increase-sales-and-revenue/

https://www.modernpostcard.com/knowledge/articles/turn-old-customers-into-new-ones

https://www.quantumpostcards.com/blog/-how-to-use-direct-mail-to-reach-your-inactive-customers

https://www.outboundengine.com/blogs/its-not-them-its-you-why-email-marketing-blasts-dont-work/

https://www.iwco.com/blog/2015/02/11/winning-back-customers-with-direct-mail/

https://www.entrepreneur.com/article/242731