Corona virus, China major city lockdowns, etc.

[Eduardo-]

Ideally, yes. Even a book is considered secondary material. Those videos people keep posting aren't even considered grey material.

I didn't know that you were so advanced. Only scientific papers for you. And you for us, for all you say you will backup it with a scientific paper also?

That's true, but you can remedy that: Cite your sources.

The sources has been always there. You are lazy to go and check, and that's what really happened. That's not my fault.