Exists or existed
Hello dear native speakers
Consider the following condition :
I read a newspaper yesterday and now I'm giving an account of what I read on different pages to my friend.Are these sentences OK ?
I'm not sure about the tenses.
On page 7, an unknown researcher tried (tries) to describe two powerful drugs in terms of how they attack (would attack) cancer cells. He concluded that there were (are) several points of similarity between the two cases. However, he added that some uncertainty still existed (exists) about the safety of these two new anti-cancer drugs.
I'm uncertain about the tenses.
For example :
He added that some uncertainty still existsted....
Since the act of reading the newspaper was related to the past, then the verb "add" should be "added" . Right? How about "exist"?
Thanks in advance