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.

Chapter 62.
At this point in the timeline, the Thain's study is still next door to the Thain's apartments, deep in the Great Smials. On Pippin's return from Buckland, leading into the start of At the End of His Rope, the Thain's coach upsets, and Pippin is trapped underneath the overturned coach and seriously injured. To bolster his spirits, Regi has a parlour on the outermost face of the Great Smials, with large windows and a panoramic view, made over into Pippin's study later in the year. See At the End of His Rope for more.