By Common errors, Whom

The CGEL notes that has been used in this manner for about 300 years. How could it even be suggested that it's incorrect? That would make singular and all the other changes that have occurred in language over the centuries also incorrect. Leaving aside the 'was/were' case, I wonder whether...

Dear sir, I have some inquiries about the choice of noun form (singular or plural) to be used with a plural possessive determiners (their, our, etc.) I have sought the advice of some native speakers on the following 4 sentences only to become more confused as they have different opinions. It is...