Interstitial Passages

A collected future history series is enhanced by new introductions and interstitial passages. This post summarizes:

Heinlein
Asimov
Blish
Herbert
Anderson (three times)
Aldiss (twice)

Heinlein's Future History has:

an elaborate Time Chart;
a Note on Untold Stories;
a very brief fictional quotation as an introduction to "Universe."

Asimov's Foundation series quotes the Encyclopedia Galactica which is compiled by the (First) Foundation.

Three volumes of Blish's Cities In Flight are introduced by a future historian who, we eventually realize, must live in a subsequent universe.

Herbert's Dune series similarly quotes future historical texts, some by "Pander Oulson."

Sandra Miesel wrote interstitial passages for Anderson's Psychotechnic History from the point of view of a future historian.

Hloch of Stormgate Choth introduces the stories in The Earth Book Of Stormgate but not those in the rest of the History of Technic Civilization.

In six numbered "Interludes" between the seven chapters of Tales Of The Flying Mountains and also in a Prologue and an Epilogue, a group of extra-solar colonists discusses how to present their earlier history of asteroid colonization and independence from Earth to their children.

Brian Aldiss' italicized interstitial passages are a major literary feature of his Galaxies Like Grains Of Sand, e.g.:

"The trees fall year by year, the mountains tumble, the galaxies burn out like tall tallow candles. Nothing is intended to last - except time."
-Brian Aldiss, Galaxies Like Grains Of Sand (London, 1979), p. 19.

(The concluding volume of Cities In Flight is The Triumph Of Time.)

Aldiss' second italicized passage lists instinct, fear, lust and conscience as factors lying behind war-causing political issues and states that they "...stem from the long and savage past of the race...," (p. 21) thus echoing Anderson's "protean enemy" in the Psychotechnic History.

I have twice quoted with approval a beautiful three-word sentence in an italicized passage of Aldiss' later Helliconia Trilogy.