I have a figure with four subfigures, each corresponding to a subcase in a theorem, labeled (a), (b)i, and (b)ii respectively using the enumitem
package (see MWE and illustration below; note the reference style in the paragraph following the theorem).
MWE:
\documentclass[a5paper]{scrartcl}
\usepackage{enumitem}
\setlist[enumerate,1]{label=\textnormal{(\emph{\alph*})}}
\setlist[enumerate,2]{labelindent=2\parindent,
label=\textnormal{(\emph{\roman*})},ref=\theenumi\textnormal{\emph{\roman*}}}
\usepackage{subcaption}
\newtheorem{theorem}{Theorem}
\begin{document}
\begin{theorem}
There are two cases and three subcases in this theorem:
\begin{enumerate}
\item \label{itm.a} About the first figure.
\item About the other figures.
\begin{enumerate}
\item \label{itm.bi} About the second figure.
\item \label{itm.bii} About the third figure.
\end{enumerate}
\end{enumerate}
\end{theorem}
The theorem talks about \ref{itm.a}, \ref{itm.bi}, and \ref{itm.bii}.
See Figures~\ref{fig.a}, \ref{fig.bi}, and \ref{fig.bii}.
\begin{figure}
\begin{center}
\begin{subfigure}[t]{0.3\textwidth}
\centering
A
\caption{The first picture} \label{fig.a}
\end{subfigure}
%
\begin{subfigure}[t]{0.3\textwidth}
\centering
BI
\caption{The second picture} \label{fig.bi}
\end{subfigure}
%
\begin{subfigure}[t]{0.3\textwidth}
\centering
BII
\caption{The third picture} \label{fig.bii}
\end{subfigure}
\caption{Three different pictures.}
\end{center}
\end{figure}
\end{document}
Since each of the subfigures corresponds exactly to one subcase in the theorem, I would like the subfigures to be labeled the same as the corresponding subcases, i.e., (a), (b)i, and (b)ii, and the references to these figures should be displayed as such as well. Specifically, I want the subfigure labels to be (a), (b)i, and (b)ii (instead of (a), (b), and (c)), and thus the last paragraph of the document with the references should read "See Figures 1(a), 1(b)i, and 1(b)ii."
How can I do this? I guess the larger question is how to make two different things have the same label.