[NTG-context] bold math

Ahoj, On November 11 I asked the list how I could generate bold greek math symbols (I have the lucida family installed). Until now I didn't get a response, so maybe I should be more specific. Let me put it this way: On page 12 of the `Fonts in ConTeXt' manual I find the footnote: `Bold math is already prepared in the core modules, so normally one can do with less code.' Can anybody tell me what code I have to add and where? I would like to get the following line $\theta = {\bfmath \alpha' x}$ with \theta in normal math and \alpha and x in math boldface? Sytse Knypstra