The other day, I looked into the slots of my checkbook to see if I had any stamps. I did, not but I found items related to three booksellers no longer in business:
A record of sales from Chapters; after a certain amount spent there, one got a discount.
A receipt for store credit at Olsson's.
A Borders gift card.
Chapters and Olsson's were linked in a way: the founders of Chapters worked at Olsson's--before it was officially called that, if I remember correctly, and probably while they were still students at Georgetown.