\documentclass[11pt,notitlepage]{amsart}
\usepackage{amsmath,graphicx,amssymb,xcolor,stmaryrd,amscd,multicol,txfonts}
% Following http://tex.stackexchange.com/a/847/22475:
\usepackage[setpagesize=false]{hyperref}\hypersetup{colorlinks,
  linkcolor={blue!50!black},
  citecolor={blue!50!black},
  urlcolor=blue
}
\def\myurl{http://www.math.toronto.edu/~drorbn/}

\paperwidth 7in
\paperheight 9.5in
\textwidth 7in
\textheight 9.5in
\oddsidemargin -0.25in
\evensidemargin \oddsidemargin
\topmargin -0.25in
\headheight 0in
\headsep 0in
\footskip 0in
\parindent 0in
\setlength{\topsep}{0pt}

\def\im{{\operatorname{im}}}

\def\qed{{\hfill\text{$\Box$}}}

\begin{document}\thispagestyle{empty}

\parbox[b]{4.1in}{\tiny
  \footnotesize\url{http://drorbn.net/?title=14-1100}
  \newline\bf\tiny
  \href{\myurl}{Dror Bar-Natan}:
  \href{\myurl/classes/}{Classes}:
  \href{\myurl/classes/\#1415}{2014-15}:
  \href{http://drorbn.net/?title=14-1100}{MAT 1100 --- Core Algebra}:
}
\hfill\parbox[b]{2.7in}{
  \null\hfill{\Large\bf Cheat Sheet Finite Groups}
}

\vskip -3mm
\rule{\textwidth}{1pt}
\vspace{-8mm}

\begin{multicols}{2}

Groups, silly uniquenesses, $(ab)^{-1}=b^{-1}a^{-1}$. $S_n$, $\sigma\tau=\sigma\circ\tau$. ``Category'', homomorphisms, $\varphi\colon S_4\to S_3$, subgroups, $\ker$, $\im$, isomorphisms. $x^g\coloneqq g^{-1}xg$. Kernels are normal, cosets, $G/N$, every normal subgroup is a kernel. $C_G(X)$, $Z(G)$, $N_G(X)$. {\bf $\mathbf 1^{\mathbf st}$ iso.} $\phi\colon G\to H$ morphism $\Rightarrow$ $G/\ker\phi\simeq\im(\phi)$.

\end{multicols}

\vskip -3mm
\rule{\textwidth}{0.75pt}
\vspace{-8mm}

\begin{multicols}{2}

{\bf Groups of small order.}

{\bf Order 0:} $\emptyset$.
{\bf Order 1:} $G_{1,1}=\{e\}$.
{\bf Order 2:}

\end{multicols}

\vfill

\parbox[b]{3.9in}{\tiny
  \footnotesize\url{http://drorbn.net/?title=14-1100}
  \newline\bf\tiny
  \href{\myurl}{Dror Bar-Natan}:
  \href{\myurl/classes/}{Classes}:
  \href{\myurl/classes/\#1415}{2014-15}:
  \href{http://drorbn.net/?title=14-1100}{MAT 1100 --- Core Algebra}:
}
\hfill\parbox[b]{3in}{
  \null\hfill{\Large\bf Cheat Sheet Rings \& Modules}
}

\vskip -3mm
\rule{\textwidth}{1pt}
\vspace{-8mm}

\begin{multicols}{2}

dsagf

\end{multicols}

\vfill

\end{document}
\endinput