We questioned whether a preposition before another preposition is gramatically correct or not two days ago here.
After that, We've got a lot of answers of how to analysing that structure in many ways. :-)
Now we will post our conclusion about that, and of course we want another feedback from you.
Please help us one more time. ;-)
We concluded our research about the English grammar

concerning preposition after a preposition.
1. prepositions don't necessarily have to govern noun phrases only.

Some prepositions can also govern a prepositional phrase.

Such prepositions are "from" and "until".
ex) He came to and knocked the burning cigarette end from between his fingers.
ex) This decision will have to wait until after the summer break.
2. First I thought that after the preposition "from", only prepositionalphrases about a place can come. But this is not true.

ex) This decision will have to wait until after the summer break.

ex) Choose your wife from among your relatives.
3. Among the prepositional phrases that are governed by a preposition, theones about place can also be subjects of a verb.
ex) Under the bed is a nice place to hide.
It would be a great help for me if some of you native speakers of English will give me some feedback on my conclusion.
If you think there are exceptions to my conclusions, please write me a reply about it.
In our last episode,
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the lovely and talented Curious G
broadcast on alt.usage.english:
We questioned whether a preposition before another preposition is gramatically correct or not two days ago here. After that, We've ... feedback on my conclusion. If you think there are exceptions to my conclusions, please write me a reply about it.

4. Some things which appear to be prepositions are actually particlesof phrasal verbs:
"He stands out in a crowd."
"Out" is part of the phrasal verb "stand out."
"He sleeps in on Tuesdays."
"In" is part of the phrasal verb "sleep in."

Lars Eighner finger for geek code (Email Removed) http://www.io.com/~eighner / "The very essence of the creative is its novelty, and hence we have no standard by which to judge it." Carl R. Rogers, On Becoming a Person
We questioned whether a preposition before another preposition is gramatically correct or not two days ago here. After that, We've ... want another feedback from you. Please help us one more time. ;-) We concluded our research about the English grammar

Please remember that asking in a.u.e. about grammar isn't research. We're pretty reliable what expressions are used or not in our dialects, but I don't know that any of the people who answered you are competent to explain an anomalous usage like "from under the bed". (It's possible that some have that competence and I don't know it. They'd probably be the people who disagreed with me.) Indeed, I don't know whether linguists have any kind of consensus on this matter.

Your conclusions below more or less agree with what I said, but a linguist might say that what I said was oversimplified, something like a correct approach but naive and conceptually flawed, or just plain wrong.
The Totally Unofficial AUE Linguist these days is Prof. John Lawler, and the grammar book he always recommends is The Syntactic Phenomena of English , in two volumes, by James D. McCawley. One of these days I may try to read it.
concerning preposition after a preposition.

(snip what I agree with, as usual)
3. Among the prepositional phrases that are governed by a preposition, the ones about place can also be subjects of a verb. ex) Under the bed is a nice place to hide..

Not necessarily about place: "After the summer break would be a great time for us to take care of that."
I'd consider any of the above example sentences very informal. I'm more likely to use the time ones than the space ones.

Jerry Friedman
Teachers: We supply a list of EFL job vacancies
2. First I thought that after the preposition "from", only prepositional phrases about a place can come. But this is not true. ex) This decision will have to wait until after the summer break.

This sentecne does not contain the preposition "from".
ex) Choose your wife from among your relatives.

I don't think this one does either it seems to me that "from among" is serving as a single preposition here.

Mark Brader "Look, sir, we can't just do nothing." Toronto "Why not? It's usually best." (Email Removed) Lawrence of Arabia