Citation Hunt

The Wikipedia snippet below is not backed by a reliable source. Can you find one?

Click I got this! to go to Wikipedia and fix the snippet, or Next! to see another one. Good luck!

In page Letterboxing (hobby):

"

The first Dartmoor letterboxes were so remote and well-hidden that only the most determined walkers found them, allowing weeks to pass before the letter made its way home. Until the 1970s there were no more than a dozen sites around the moor, usually in the most inaccessible locations. Increasingly, however, letterboxes have been located in relatively accessible sites and today there are thousands of letterboxes, many within easy walking distance of the road. As a result, the tradition of leaving a letter or postcard in the box has been forgotten.[citation needed]