I'm working on a post listing principles for when the plural form of a verb is needed to agree with its subject.
My basic reference is CMOS, and I can tell you, it is not a task which Sherlock Holmes would describe as "elementary". :(
The SOL editor is too basic to be practical for making revisions to a lengthy post, but I'll want to post some drafts here to see how they appear, which I'll then delete.
Please wait before adding your comments until after I've added a brief third post stating I've completed what will be, at best, a 'discussion document'.
It would be helpful if anyone could send me copies of, or links to, other references which provide advice on when verbs should be singular or plural. If you know of any, please email them to me at email@example.com. (I am more likely to notice those arriving than anything sent via the SOL mail system.)