>"The invariable indicators...agency officers usually had more than one working foreign language, their cover was usually as a “political” or “consular” official (often vice-consul); internal embassy reorganizations usually left agency personnel untouched"

Reading stuff like this is really irritating. Do the author and editors not know the meaning of "unchanging and invariable"? It just makes the entire article seem idiotic.

Outside of formally defined abstract systems, "invariant" almost always means "usual"

I am a native English speaker and have never heard someone use "unchangeable" or "invariable" to mean anything other than the correct meaning: "not variable; not changing or capable of being changed; static or constant."

And "impossible" means "difficult". I believe this feature of natural language is called hyperbole, and its study is part of the Linguistics subfield of Pragmatics.

I was looking for a list of those 26 indicators and found this article:

https://lunghu.wordpress.com/tag/yuri-trotov/

If your looking for indicators of surveillance teams, we've got quite a bit on it in Umbrella.

https://play.google.com/store/apps/details?id=org.secfirst.u...