# Referencing to a theorem using \cite and memoir [duplicate]

I am citing a book, and I would like to reference a specific theorem within that book. Usually, I would use something like

\cite[Theorem~4]{Reference}

which would have produced something like [1, Theorem 4] as an output. However I am using the memoir document class, and when I try to do that I get the following error:

! Argument of \@citex has an extra }.

Is there any way to circumvent this without too much pain?

(Removing the [Theorem~4] part from the code works just fine.)

• (1) welcome, (2) please provide a full minimal example so we get a better clue of what you are doing. Memoir has no problem with the syntax you provide, so something else must be wrong. To figure it out we need more information – daleif Jan 31 '16 at 20:59
• If this is in the optional argument to a theorem-like environment, you should protect it with braces: \begin{thm}[{\cite[Theorem~4]{key}}] – egreg Jan 31 '16 at 21:21
• @egreg: That solved it! If you post it as an answer, I will accept. – user97199 Jan 31 '16 at 21:25
• It's a duplicate; don't worry: searching the site is difficult even for regulars. – egreg Jan 31 '16 at 21:29