\documentclass[12pt]{article}
\usepackage[centertags]{amsmath}
\usepackage{amsfonts,amssymb,amsthm}
%
%PAGE REFORMATTING
%
\setlength{\topmargin}{0 in}
\setlength{\headheight}{0.25 in}
\setlength{\oddsidemargin}{0.5 in}
\setlength{\textwidth}{6 in}
\setlength{\textheight}{8.5 in}
\setlength{\headsep}{0.25 in}
\newcommand{\singlespaced}{\renewcommand{\baselinestretch}{1}\normalfont}
\newcommand{\doublespaced}{\renewcommand{\baselinestretch}{2}\normalfont}
\singlespaced
\doublespaced
%
%THEOREM STYLES
%
\theoremstyle{definition}
\newtheorem{defn}{Definition}[section]
\newtheorem{fig}{Figure}[section]
%
\theoremstyle{plain}
\newtheorem{res}[defn]{Result}
\newtheorem{thm}[defn]{Theorem}
\newtheorem{cor}[defn]{Corollary}
\newtheorem{prop}[defn]{Proposition}
\newtheorem{lem}[defn]{Lemma}
%
\theoremstyle{remark}
\newtheorem*{case}{Case}
\newtheorem{rem}[defn]{Remark}
\newtheorem{ex}[defn]{Example}
\newtheorem{exs}[defn]{Examples}
%
%EQ. NUMBERING
%
\numberwithin{equation}{section}
\renewcommand{\theequation}{\thesection.\arabic{equation}}
%
\def\thetitle{The Name of My Thesis}
\def\theauthor{John Doe}
\def\theadvisor{Advisor: My Advisor}
\def\theyear{The Year}
%
\pagenumbering{roman}
\begin{document}
\include{Titlepage}
\include{Abstract}
%\include{Dedication}
\pagenumbering{arabic}
\pagestyle{myheadings} \markright{}
\include{Chap1}
...
\include{Chapn}

\begin{thebibliography} \small
%
\bibitem[Euc]{Euc} Euclid, The Elements, BC
%
\end{thebibliography}
\end{document}

