How to display read articles?

[Angel de Vicente]

Hi,

I just decided to switch to Gnus for my news/mail experience, and I'm
learning how to do different things with it. One thing that I have not
managed to do (forgive me, it's pretty late here) is to view read
articles in the summary buffer. 

I mean: after reading some articles, I exit the summary buffer, then
later on I enter the group again, and the read articles are gone. I know
that they are not deleted, and I've trying to find the option to let me
see all the messages in a group (regardless of whether they had been
read or not), but could not find it in the documentation. I'm sure it is
somewhere in there, but the number of available options in Gnus is just
overwhelming....

Thanks,
Ángel de Vicente