Chapter 28.
The speed of the messenger horse was calculated from the following fascinating web pages:

http://www.ultimatehorsesite.com/info/horsespeedmph.htm
http://www.ultimatehorsesite.com/info/farandfast.html

Chapter 31.
The conversation that takes place early in the chapter is set right after the first chapter of All that Glisters.

Chapter 52.
Ferdi and Farry finding the Thain's treasure is recounted in StarFire.

Chapter 54.
Frodo and Merry evicted "three young hobbits (two Boffins and a Bolger) who were knocking holes in the walls of one of the cellars" and Frodo "had a tussle with young Sancho Proudfoot ... who had begun an excavation in the larger pantry, where he thought there was an echo" after Bilbo's departure in "A Long-Expected Party" in The Fellowship of the Ring.

Final Note.
The earlier story, A Matter of Appearances, was taken offline for some months for editing. It has now been restored.