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 Uniform Penny Post:

"

In his proposal, Hill also called for official pre-printed envelopes and adhesive postage stamps as alternative ways of getting the sender to pay for postage, at a time when prepayment was optional.[2] Previously, postage had depended on distance and the number of sheets of paper; now, one penny would assure delivery of an envelope and the letter it enclosed anywhere in the country provided together they satisfied the weight condition. This was a lower rate than before, when the cost of postage was usually more than 4d (four pence). The reform did not settle the issue of who paid for the postage, as it still remained optional for a number of years in spite of Hill's efforts as Secretary to the Post Office to alter the situation.