Can anyone give me examples of the relative-determinative 'which'?
I recently posted a question on a Spanish language forum asking what the equivalent in Spanish would be for the use of which in a phrase such as
he refused, which decision proved disastrous
(which comes from the Oxford English/Spanish dictionary)
Someone on the forum is saying that this use of which is incorrect English, and that this fragment is in some way artificial, and would never occur in a correct English sentence.
I can easily think of sentences such as
The king refused his support for this endeavour, which decision left the duke without aid.
It's a formal, perhaps unusual, use, but perfectly good English.
Can anyone point me to examples online which would back this argument? I can't find any except in the Free Dictionary (https://www.thefreedictionary.com/which), definition 10, which is not quite the same thing. Also, perhaps, a pointer to the grammatical rule which defines this usage of which this is an example.
Edit: someone in the Spanish language forum pointed out this entry -- https://languagelog.ldc.upenn.edu/nll/?p=606 -- which points out that this is a 'relative-determinative' usage. Any other links would be welcomed!
Thanks very much!
Edit: This was the entry from which I drew my example. I don't know whether it's correct or not, or whether it was the intention of Oxford to present it as a fragment or as a whole sentence, but it does exist. From the Oxford Spanish/English dictionary that comes bundled with the Mac OS. Entry for adjective, 2a 
Solution 1:
Well, if you're just looking for usage examples, it's easy enough to do a Google search for the phrase "which decision proved," which method will give you quite a few examples. (They will include many quotations of a passage from Little Women involving a "second tumble down the beanstalk.") Of course, you can also substitute different nouns and verbs for "decision" and "prove," which tactic will give you all sorts of additional evidence to cite.
Solution 2:
You will probably find many results if you search for relative adjective, which term you will find in Merriam–Webster and elsewhere:
Relative adjective: a pronominal adjective that introduces a clause qualifying an antecedent (as which in:
“our next meeting will be on Monday, at which time a new chairman will be elected”
) or a clause functioning as a substantive (as which in
“I do not know which course I should follow”
).
(Their second example might arguably be called an interrogative adjective or similar.)
This is indeed perfectly good English, nor is it very uncommon. Be paranoid in linguistics whenever someone tells you x is "never used"!
Other terms are attributive relative (pronoun) and adjectival relative (pronoun).
Solution 3:
Oxford's online English-Spanish dictionary has the exact same example you mention:
which
cuál, pron.Pronunciación
/(h)wɪtʃ//wɪtʃ/ADJETIVO
2 2.1 (as relative)
we arrived at two, by which time they had gone — llegamos a las dos y para entonces ya se habían ido
Más frases de ejemplo
in which case — en cuyo caso
he refused, which decision proved disastrous — se negó, decisión que resultó desastrosa
Screenshot just in case they change the examples from time to time.
I also found a similar usage with "refused" in an online article:
The construction manager at the site offered the rigging contractor “a set of fresh slings for the job”, but he refused, which decision led to the accident.
Source
And another one with "declined", which is a synonym of "refused" when used in the same way as an intransitive verb:
His Honour declined, which decision was affirmed on appeal.
Source
It doesn't seem to be a common usage, and it also looks tied to legal texts, but the examples are there.
There may be more usages like these if you search for other variants: action instead of decision, conceded instead of refused, etc.