except that the subordinators where, wherever, as [manner] and as soon as are excluded.

[diamondcutter]

Clauses with an -ing participle maybe introduced by any of the subordinators for -ed participle clauses, except that the subordinators where, wherever, as [manner] and as soon as are excluded.
Source: A Comprehensive Grammar of the English Language by Randolph Quirk, Sidney Greenbaum, Geoffrey Leech.

This sentence looks a little odd to me. It uses “except” and “excluded” in one sentence that way. What about just saying this?
Clauses with an -ing participle maybe introduced by any of the subordinators for -ed participle clauses, except the subordinators where, wherever, as [manner] and as soon as.

 

[jutfrank]

You're correcting Randolph Quirk's grammar? If only he were still alive to hear your suggestions.

 

[diamondcutter]

Thanks for your reply, Jutfrank.
I didn't mean to do that. If Randolph Quirk's knowledge of English is like the Pacific Ocean, mine is just like a cup of water. Limited by my English level, I didn’t express myself clearly. I should have said I didn’t quite understand that sentence and whether you could paraphrase it for me.

 

[jutfrank]

I was just teasing you. Yes, you've understood the sentence correctly.