En réponse à Tristan <[log in to unmask]>: > > Is there a standard way of doing that? We've been told to do f^(9) > (differentiated from f^9 by naught but brackets), because f'''' is > already ridiculous enough.... > f^(9) *is* the standard way to do it. I was also taught that way. Andreas's teacher's "f^IX", though not unknown is pretty much non-standard (and not very practical anyway. I can't see in what way f^III is an improvement over f''' ;)))) ). I've occasionally seen it, but among people that regularly underline vectors even in print, instead of writing them in bold letters! :)) Hehe, the mathematical typographic standards are like X-SAMPA on the list: everybody has his/her own substandard way of using them ;)))) . Christophe. http://rainbow.conlang.free.fr It takes a straight mind to create a twisted conlang.