\documentclass[11pt]{article}
\usepackage{url}
\urlstyle{same}
\usepackage{amsmath}
\usepackage[top=1.5 in, left=1.5 in, bottom=1.5 in, right=1.5 in]{geometry}
\usepackage{graphicx}
\setlength{\marginparwidth}{1.2in}
\newcommand{\margin}[1]{\marginpar{\raggedright \tiny #1}}
\setlength{\parindent}{0in}
\setlength{\parskip}{+.2in}

\begin{document} 
\title{Example of Bibliography, URL, and Abstract}
\author{George Francis}
\maketitle
\begin{abstract}
Note that to see [?] replaced by actual numbers [1] you need to typeset the
file twice. LaTeX creates an auxillary file the first time, and uses it the second.
Read the comented out explanations at the bottom. While the bibliography
\margin{Marginal notes are very useful during the preparation of a document when there is an editor or co-author who has comments.}
functions used here are built into LaTeX, you'll need the url package for
writing nice web references. A proper web reference includes the author of
the webpage, if you can find it. And it includes the date of your last 
access because web references are mutable and not very long lived. 
\end{abstract}
{\bf Theorem.  }\cite{APERY}{\it For all real numbers $x$ and $y$, $$|xy|=|x||y|$$.}
{\bf Proof.} To prove 
this\footnote{\url{http://new.math.uiuc.edu/this_is@test}},
first suppose that $x \ge 0$ and $y \ge 0$.  
Then $xy \ge 0$.
By definition\cite{brocket-1982} of absolute value, $|xy| = xy$, $|x| = x$ and $|y|=y$. 
Therefore $|xy| = |x| |y|$.

Having considered all possible cases\cite{BT}
for the signs of $x$ and $y$, we have proved that $|xy| = |x| |y|$.
\hfill q.e.d.

This proof is of importance because it establishes that absolute value 
commutes with multiplication, a commonly used property of absolute value.
The proof\cite{bt} illustrates the strategy of dividing a mathematical statement into
several cases and proving each case separately.


\begin{thebibliography}{ABC}

\bibitem{APERY} F.~Ap\'ery.\emph{ An algebraic halfway model
for the eversion of the sphere.} Tohoku Math. J. \textbf{44} (1992). 
pp. 103-150 with an appendix by Bernard Morin.


\bibitem{BALOG}
Z.M. Balogh, R.~Hofer-Isenegger, and J.T. Tyson.
\emph{Lifts of {L}ipschitz maps and horizontal fractals in the
  {H}eisenberg group,} Ergodic Theory Dynam.\ Systems \textbf{26}
(2006), 621--651.

\url{http://new.math.uiuc.edu/this_is@another^test }

\bibitem{BT}
Z.M. Balogh and J.T. Tyson.
\emph{Hausdorff dimensions of self-similar and self-affine fractals in
  the {H}eisenberg group,} Proc.\ London Math.\ Soc.\ (3) \textbf{91}
(2005), no. 1, 153--183

\bibitem{brocket-1982}
R.~W. Brockett.
\emph{Control theory and singular {R}iemannian geometry}, in ``New
directions in applied mathematics'' (Cleveland, Ohio, 1980),
Springer-Verlag, 1982, 11--27.
  
\end{thebibliography}

\end{document}

%Note that you cite the reference in the text where you want to see the citation.
%TeX will number them consecutively even if the order in the bibliography is 
%not the same, and after  deleting a \cite. But the article stays in the 
%References section until you delete the unused reference..
%You should never have something in the References that isn't actually cited!
%Note also that the citation tag is case sensitive. The last \cite{bt} will
%always leave a [?] and not be properly processed.