https://www.google.com/books/edition/Type_Logical_Syntax/ML7...
The name center embedding comes from the fact that the relative clause is embedded after the nominal subject head and before the VP.
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https://www.google.com/books/edition/Narrative_Complexity/-u...
Consider sentences 1 and 2 below. The first is right branching, the second center embedded.
1. The man drove the car that hit the dog that died.
2. The dog the car the man drove hit died.
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https://www.google.com/books/edition/Human_Language/Xr60DwAA...
A well-known construction is center embedding, where several (of the same type of) structures nested inside one another make sentences increasingly difficult to process. . . .
(7) a. The intern [who the nurse supervised] had bothered the administrator [who lost the medical reports].
b. The administrator [who the intern [who the nurse supervised] had bothered] lost the medical reports.
Sentence (7b) has been shown to be considerably more difficult to process . . .
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https://www.google.com/books/edition/Encoding_and_Navigating...
[An example of multiple center-embedding that tends to be prohibitively confusing]:
The patient the nurse the clinic had hired admitted met Jack.
[An example of a sentence "with two degrees of center-embedding" that "can still be comprehended under certain conditions"]:
The reporter who everyone that I met trusts said the president won't resign yet.
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https://www.google.com/books/edition/The_Origins_of_Grammar/...
'The typical center-embedded clause is a relative clause' (p. 374). One firm constraint is 'Double relativization of objects (The rat the cat the dog chased killed ate the malt) does not occur (p. 365). An example of a centre-embedded clause (underlined here) at depth 2 (C^2) in Karlsson's notation) is "She thought that he who had been so kind would understand." This is centre-embedded because there is material from its superordinate clause before it (he) and after it (would understand). . . .
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Others not quoted:
https://www.google.com/books/edition/English_Grammar/Lem4miC...
https://www.google.com/books/edition/Encyclopedia_of_Languag...
https://www.google.com/books/edition/Syntax/1U4gAwAAQBAJ?hl=...
https://www.google.com/books/edition/The_Handbook_of_Linguis...