Three Substantial Volumes

The scope and scale of Poul Anderson's History of Technic Civilization is shown first by the fact that the History published in chronological order of fictitious events fills seven omnibus volumes in Baen Books' The Technic Civilization Saga and secondly by the fact that some pre-Saga collections comprise substantial series in their own rights. Thus:

The Earth Book Of Stormgate, as I have said more than once before, completes the history of the Polesotechnic League, almost completes the history of human-Ythrian interactions and is a future history;

The Night Face And Other Stories covers the entire post-Imperial period of the Technic History and is a future history;

The Imperial Stars had the same contents as The Technic Civilization Saga, Volume IV, Young Flandry, and therefore covered Dominic Flandry's early career from Ensign to Commander before he became the central character of the previously published Captain Flandry series.

And these three volumes in no way encompass the entire Technic History.

Addendum: I have read an on-line review which states that The Imperial Stars also collects The Day Of Their Return.