"Manuals-ConTeXt wiki" provides us very important and useful
information and we find cont-eni.pdf in "overview". In the manual,
font switching commands \vi, \vii, \viii, \ix, \x, \xi, \xii are
explained in p.113 but it seems they don't work except \vi and \xi.
>From my simple test with ConTeXt, \xi produces a greek letter "ξ"
as in traditional TeX and \vi seems to do nothing.
Is the above explanation obsolete or is additional setup necessary?
I'd like to know what is the real situation of these commands.
Thanks in advance.