[NTG-context] Theorems with arguments like amsthm

Hi, I have my environment of context that defines the theorems and lemmas like amsthm in latex. For example, for lemmas, I have: \defineenumeration [lemma] [text={Lemma},headstyle=bold,between=\blank,titledistance=0em,textdistance=1em, stopper={.\space},location=serried,left={\bgroup\bf},right={\egroup},width=fit,style=italic] The question is how can I get the typical argument of lemmas: "Lema 4.1 (superadditive lemma)"? How can I add the possibility that lemma _could_ have one argument (the phrase in parentesis)?. I'm not a TeX programmer, such a ConTeXt user. Any hint? Thanks, Xan.