1\documentclass{article}
2
3\newif\iflatextortf
4\latextortffalse  %ignored by latex2rtf
5
6\iflatextortf
7\else
8\makeatletter
9\DeclareRobustCommand*\textsubscript[1]{%
10 \@textsubscript{\selectfont#1}}
11\newcommand{\@textsubscript}[1]{%
12 {\m@th\ensuremath{_{\mbox{\fontsize\sf@size\z@#1}}}}}
13\makeatother
14\fi
15
16\begin{document}
17
18This text is nonsense but only written to make the use
19of \verb#\textsuperscript{-17}# visible.
20Here it comes: 10 to -17 should be 10\textsuperscript{-17}.
21
22And this is what mathmode would display: $10^{-17}$
23
24The same for subscript. \verb#\textsubscript{x}# isn't (yet)
25implemented in standard \LaTeX\ or \LaTeXe, but it is easy to
26add. The definition in the preamble of this document was
27suggested in the newsgroup comp.text.tex and works similar
28as \verb#\textsuperscript{x}# which is fully supported part of \LaTeXe.
29
30Does \verb#\textsubscript{8}# work?
31Here it is: 10 index 8 should be 10\textsubscript{8}.
32
33And the same in mathmode: $10_{8}$
34\end{document}
35