[NTG-context] tables

Does someone knows where there is information on the table environment in ConTeXt? I have read the intro on ConTeXt and the pamphlets from the Pragma-site on tabulate and btable, but there seem to be a lot more options than can be found in these; I encountered something like \AR etc. whose effects I could not figure out with some tests. Also there is some mention of Wichura's manual. Is this somewhere to be found on the internet? Thanks in advance. Hans van der Meer