[NTG-context] Some symbols of mathematical calculus missing?

Hi all, I need to typeset some equations and I found out that these commands are undefined or don't work correctly (ver: 2009.04.17 19:32 MKIV): \iint, \iiint, etc. \oint, \oiint, etc. \nabla What is the prefered way of typesetting those symbols? (e.g. \mathop{\int \!\!\! \int} or something like that?) Is there a website or a pdf-file dealing with mathematical symbols in ConTeXt? Thanks Tomas