Grouping 2 subfigure and 1 other figure (subfigure within a subfgure)

Question

I have 3 figures to be put in a figure which spans over a single column in a two-column document. The first two subfigures are similar and should be grouped together with labeling a(i) and a(ii) and the third subfigure should have a label of (b). I am using \subfigure command as follows. Is there a way to arrange the first two figures within one more subfigure and the third one in a separate subfigure? Currently I am getting the labels as (a) , (b) and (c) Something like this:

Code:

\begin{figure*}[] % not h only
\centering
\subfigure[a(1)]{%
\includegraphics[width=0.3\textwidth]{figa1.pdf}%
\label{figa1}%
}\hfil
\subfigure[a(2)]{%
\includegraphics[width=0.3\textwidth]{figa2.pdf}%
\label{figa2}%
}

\subfigure[b]{%
\includegraphics[width=0.38\textwidth]{figb.pdf}%
\label{figb}%
}

\caption{Overall title }
\label{fig1}
\end{figure*}

Answer 1

Here is my suggestion using the subcaption package:

\documentclass[twocolumn]{article}
\usepackage[demo]{graphicx} % do not use the demo option in actual document
\usepackage{subcaption}
\begin{document}

\begin{figure*}
  \begin{subfigure}{0.6\textwidth}
  \captionsetup[subfigure]{labelformat=simple}
    \begin{subfigure}{0.5\textwidth}
      \renewcommand\thesubfigure{\alph{subfigure} (i)}
      \centering
      \includegraphics[width=.95\textwidth]{figa1.pdf}
      \caption{}
      \label{fig:figa1}
    \end{subfigure}%
    \begin{subfigure}{0.5\textwidth}
      \addtocounter{subfigure}{-1}
      \renewcommand\thesubfigure{\alph{subfigure} (ii)}
      \centering
      \includegraphics[width=.95\textwidth]{figa2.pdf}
      \caption{}
      \label{fig:figa2}
    \end{subfigure}%
  \end{subfigure}%
  \begin{subfigure}{0.38\textwidth}
    \centering
    \includegraphics[width=\textwidth]{figb.pdf}
    \caption{}
    \label{fig:figb}
  \end{subfigure}
  \caption{overall caption for all three subfigures}
  \label{fig:figure}
\end{figure*}
\end{document}