History of this document.

\begin{itemize}
\item Specification \textbf{Astaire} ('A'). \textit{10 October 2014}. Initial specification.
\item Specification \textbf{Bacal.} ('B'). \textit{1 November 2015}. Second release.
\item Specification \textbf{Chaplin} ('C'). \textit{31 August 2015}. Third release.
\end{itemize}
