[NTG-context] Multiple citations at one position

Hi, I am citing several references at one position in my document and I was wondering if there is a way to get something like "[1, 3, 9 - 11]" instead of "[1] [3] [9] [10] [11]" (what I would get by using "\cite[ref1] \cite[ref3] \cite[ref9] ..."). Unfortunately I can't find some deeper information about \cite or \setupcite. I'd appreciate any suggestions. Thanks in advance, Stefan.