Some of the soldiers in the "terracotta army," referred to in the meeting with Toby (Richard Schiff) and Kate (Mary McCormack), were exhibited at the National Geographic building in Washington DC and other locations in the United States in 2009-2010.
Paxton Whitehead (playing Protocol Officer Bernard Thatch) had previously appeared in the episode "Nöel" (Season 2, Episode 10) in a subplot about a Holocaust survivor who discovers that her painting, which had been looted by the Nazis, was hanging in the White House.
Toby (Richard Schiff)'s perusing of the Hoynes book is a very "Washington thing" - flip to the index and see how many entries appear after your name.