[Tex/LaTex] Numbering of subsubsections: “A.” in number, “1.1.1.A” in references

cross-referencingnumberingsectioning

I'm quite new to Latex and I'd like to achieve the following thing.

I want my document to have the following numbering structure: 

1. chapter 
1.1 section
1.1.1 subsection 
A. subsubsection.

(In the TOC I only want the chapters, sections and subsections to be listed.)

I achieved this by adding the following extra lines in the beginning of my LaTex document:

% set section numbering depth
\setcounter{secnumdepth}{3} % 3 => section, subsection, subsubsection
\setcounter{tocdepth}{2}    % 2 => section, subsection
% replace subsubsection numbering by single letter
\renewcommand{\thesubsubsection}{\Alph{subsubsection}}

Problem: when I make a reference to this subsubsection, I get something like this:

A

I want this to be formatted like this:

1.1.1.A

Best Answer

Without using additioal packages, you can simply redefine \p@subsubsection which controls the prefix used for cross-referencing subsubsection:

\documentclass{book}

\setcounter{secnumdepth}{3}
\setcounter{tocdepth}{2}
\renewcommand\thesubsubsection{\Alph{subsubsection}} 
\makeatletter
\renewcommand\p@subsubsection{\thesubsection.} 
\makeatother

\begin{document}

\tableofcontents

\chapter{Test Chapter}
\section{Test Section}
A cross-reference to some subsubsections: \ref{a}, \ref{b} and \ref{c}.
\subsection{Test Subsection}
\subsection{Test Subsection}
\subsubsection{Test Subsubsection}\label{a}
\subsubsection{Test Subsubsection}\label{b}
\subsection{Test Subsection}
\subsubsection{Test Subsubsection}\label{c}

\end{document}

Am image of the obtained ToC:

enter image description here

And an image of the document body, showing the desired formatting for the headings and the cross-references:

enter image description here

On a side (personal) note, as tohecz has already mentioned, I think this might be confusing since it introduces some level of inconsistency (the string used for the cross-references doesn't really belong to the object that is being referenced).

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