I would like to change the section/subsection style of my LaTeX document. The following is an example of what I would like:

3. Methodology and data: An explanation (Level 1. 12 font. In bold. Period after number.)

3.1. Empirical methods (Level 2. Subheading in italics NOT bold. Font size same as level 1. Periods after numbers.)

3.1.1. Testing vectors (Level 3. Subsubheading in italics NOT bold. Font size same as level 1. Periods after numbers.)

Similarly, the above section/subsection style should continue on for all subheadings.

I would like only the above changes to be applied to my entire document. I want all other section/subsection settings to remain as default (i.e, flushed left etc). Cross referencing should also remain as the default, e.g., 3.1.1. should be cross referenced as "3.1.1" (no italics and no period after the last number).

My MWE is currently:

\documentclass[twoside, a4paper, 12pt]{article}
\usepackage{ragged2e}
\usepackage{booktabs,tabularx}
\usepackage{amsfonts}
\usepackage{amsthm}
\usepackage{mathtools}
\usepackage{verbatim}
\usepackage{amsmath, amssymb}
\usepackage{natbib}
\usepackage{tikz}
\usepackage{enumerate}
\usetikzlibrary{matrix, arrows}
\usepackage{graphicx}
\usepackage{subfig}
\usepackage{listings}
\usepackage{color}
\usepackage{float}
\usepackage{multicol}
\usepackage{booktabs}
\usepackage{lscape}
\usepackage{cases}
\usepackage{multirow}
\usepackage[figuresright]{rotating}
\usepackage{setspace}
\usepackage{lscape}
\usepackage{longtable}
\usepackage{caption}
\usepackage{pslatex}
\usepackage[update,prepend]{epstopdf}
\usepackage[official]{eurosym}

\setlength{\textwidth}{6.5in}
\setlength{\oddsidemargin}{0in}
\setlength{\evensidemargin}{0in}
\setlength{\parindent}{0pt}
\setlength{\parskip}{1ex plus 0.5ex minus 0.2ex}

\usepackage[top=1in, bottom=1in, left=1in, right=1in]{geometry}

\begin{document}

\bibliographystyle{apa-good}
\bibliography{bibliography}
\end{document}

• Your MWE is not minimal. And as a side-remark: Don't use \linespread[2]. There are several reasons not to do it. You alredy did load the setspace package in your example preamble. Just call \onehalfspacing instead. – Ruben Oct 24 '13 at 14:08
• @Ruben, Thanks for that. Just wondering, does \onehalfspacing produce the same results as \linespread[2]? What is its advantage? – TrueTears Oct 24 '13 at 14:31
• You load booktabs twice! – Sveinung Oct 24 '13 at 15:30
• @TrueTears: \linespread does also affect footnotes and list environments. In most of the cases this is not desirable and setspace takes care of these things. (See also l2tabu, p. 5) And your scepticism is totally appropriate :-) Probabilly the \doublespaing macro is the analogue procedure. But I'm not completely certain about it. I would have to look this up too. – Ruben Oct 24 '13 at 15:35

titlesec is able to do what you need:

\documentclass[12pt]{article}
\usepackage{titlesec}
\titleformat{\section}
{\normalfont\normalsize\bfseries}{\thesection.}{1em}{}
\titleformat{\subsection}
{\normalfont\normalsize\itshape}{\thesubsection.}{1em}{}
\titleformat{\subsubsection}
{\normalfont\normalsize\itshape}{\thesubsubsection.}{1em}{}
\begin{document}
\section{Test}
\subsection{Test Test}
\subsubsection{Test Test Test}
\end{document}


Note: As your document will be in 12pt, I used \normalsize to get the sectioning headings to 12pt.