Sentence Correction

Hi GMAT Experts,

Can you please help me with some advanced concepts on pronoun reference. At many times I get confused with they and them. Suppose a sentence has 2 nouns both are plural how to judge reference of they pronoun ? Any good articles on pronoun reference.

Example :-

Investors heard the challenges facing the company ,including among them the threat .....

Is "them" not referring to challenges facing the company ?

Thanks in advance for your help.

There is no way to know, that is why this is improper. Would read - "... amongst these challenges the threat...

You have to be undoubtedly clear with information.