$$
% create the definition symbol
\def\bydef{\stackrel{\Delta}{=}}
%\def\circconv{\otimes}
\def\circconv{\circledast}
\newcommand{\qed}{\mbox{ } \Box}
\newcommand{\infint}{\int_{-\infty}^{\infty}}
% z transform
\newcommand{\ztp}{ ~~ \mathop{\mathcal{Z}}\limits_{\longleftrightarrow} ~~ }
\newcommand{\iztp}{ ~~ \mathop{\mathcal{Z}^{-1}}\limits_{\longleftrightarrow} ~~ }
% fourier transform pair
\newcommand{\ftp}{ ~~ \mathop{\mathcal{F}}\limits_{\longleftrightarrow} ~~ }
\newcommand{\iftp}{ ~~ \mathop{\mathcal{F}^{-1}}\limits_{\longleftrightarrow} ~~ }
% laplace transform
\newcommand{\ltp}{ ~~ \mathop{\mathcal{L}}\limits_{\longleftrightarrow} ~~ }
\newcommand{\iltp}{ ~~ \mathop{\mathcal{L}^{-1}}\limits_{\longleftrightarrow} ~~ }
\newcommand{\ftrans}[1]{ \mathcal{F} \left\{#1\right\} }
\newcommand{\iftrans}[1]{ \mathcal{F}^{-1} \left\{#1\right\} }
\newcommand{\ztrans}[1]{ \mathcal{Z} \left\{#1\right\} }
\newcommand{\iztrans}[1]{ \mathcal{Z}^{-1} \left\{#1\right\} }
\newcommand{\ltrans}[1]{ \mathcal{L} \left\{#1\right\} }
\newcommand{\iltrans}[1]{ \mathcal{L}^{-1} \left\{#1\right\} }
% coordinate vector relative to a basis (linear algebra)
\newcommand{\cvrb}[2]{\left[ \vec{#1} \right]_{#2} }
% change of coordinate matrix (linear algebra)
\newcommand{\cocm}[2]{ \mathop{P}\limits_{#2 \leftarrow #1} }
% Transformed vector set
\newcommand{\tset}[3]{\{#1\lr{\vec{#2}_1}, #1\lr{\vec{#2}_2}, \dots, #1\lr{\vec{#2}_{#3}}\}}
% sum transformed vector set
\newcommand{\tsetcsum}[4]{{#1}_1#2(\vec{#3}_1) + {#1}_2#2(\vec{#3}_2) + \cdots + {#1}_{#4}#2(\vec{#3}_{#4})}
\newcommand{\tsetcsumall}[4]{#2\lr{{#1}_1\vec{#3}_1 + {#1}_2\vec{#3}_2 + \cdots + {#1}_{#4}\vec{#3}_{#4}}}
\newcommand{\cvecsum}[3]{{#1}_1\vec{#2}_1 + {#1}_2\vec{#2}_2 + \cdots + {#1}_{#3}\vec{#2}_{#3}}
% function def
\newcommand{\fndef}[3]{#1:#2 \to #3}
% vector set
\newcommand{\vset}[2]{\{\vec{#1}_1, \vec{#1}_2, \dots, \vec{#1}_{#2}\}}
% absolute value
\newcommand{\abs}[1]{\left| #1 \right|}
% vector norm
\newcommand{\norm}[1]{\left|\left| #1 \right|\right|}
% trans
\newcommand{\trans}{\mapsto}
% evaluate integral
\newcommand{\evalint}[3]{\left. #1 \right|_{#2}^{#3}}
% slist
\newcommand{\slist}[2]{{#1}_{1},{#1}_{2},\dots,{#1}_{#2}}
% vectors
\newcommand{\vc}[1]{\textbf{#1}}
% real
\newcommand{\Real}[1]{{\Re \mit{e}\left\{{#1}\right\}}}
% imaginary
\newcommand{\Imag}[1]{{\Im \mit{m}\left\{{#1}\right\}}}
\newcommand{\mcal}[1]{\mathcal{#1}}
\newcommand{\bb}[1]{\mathbb{#1}}
\newcommand{\N}{\mathbb{N}}
\newcommand{\Z}{\mathbb{Z}}
\newcommand{\Q}{\mathbb{Q}}
\newcommand{\R}{\mathbb{R}}
\newcommand{\C}{\mathbb{C}}
\newcommand{\I}{\mathbb{I}}
\newcommand{\Th}[1]{\mathop\mathrm{Th(#1)}}
\newcommand{\intersect}{\cap}
\newcommand{\union}{\cup}
\newcommand{\intersectop}{\bigcap}
\newcommand{\unionop}{\bigcup}
\newcommand{\setdiff}{\backslash}
\newcommand{\iso}{\cong}
\newcommand{\aut}[1]{\mathop{\mathrm{Aut(#1)}}}
\newcommand{\inn}[1]{\mathop{\mathrm{Inn(#1)}}}
\newcommand{\Ann}[1]{\mathop{\mathrm{Ann(#1)}}}
\newcommand{\dom}[1]{\mathop{\mathrm{dom} #1}}
\newcommand{\cod}[1]{\mathop{\mathrm{cod} #1}}
\newcommand{\id}{\mathrm{id}}
\newcommand{\st}{\ |\ }
\newcommand{\mbf}[1]{\mathbf{#1}}
\newcommand{\enclose}[1]{\left\langle #1\right\rangle}
\newcommand{\lr}[1]{\left( #1\right)}
\newcommand{\lrsq}[1]{\left[ #1\right]}
\newcommand{\op}{\mathrm{op}}
\newcommand{\dotarr}{\dot{\rightarrow}}
%Category Names:
\newcommand{\Grp}{\mathbf{Grp}}
\newcommand{\Ab}{\mathbf{Ab}}
\newcommand{\Set}{\mathbf{Set}}
\newcommand{\Matr}{\mathbf{Matr}}
\newcommand{\IntDom}{\mathbf{IntDom}}
\newcommand{\Field}{\mathbf{Field}}
\newcommand{\Vect}{\mathbf{Vect}}
\newcommand{\thm}[1]{\begin{theorem} #1 \end{theorem}}
\newcommand{\clm}[1]{\begin{claim} #1 \end{claim}}
\newcommand{\cor}[1]{\begin{corollary} #1 \end{corollary}}
\newcommand{\ex}[1]{\begin{example} #1 \end{example}}
\newcommand{\prf}[1]{\begin{proof} #1 \end{proof}}
\newcommand{\prbm}[1]{\begin{problem} #1 \end{problem}}
\newcommand{\soln}[1]{\begin{solution} #1 \end{solution}}
\newcommand{\rmk}[1]{\begin{remark} #1 \end{remark}}
\newcommand{\defn}[1]{\begin{definition} #1 \end{definition}}
\newcommand{\ifff}{\LeftRightArrow}
<!-- For the set of reals and integers -->
\newcommand{\rr}{\R}
\newcommand{\reals}{\R}
\newcommand{\ii}{\Z}
\newcommand{\cc}{\C}
\newcommand{\nn}{\N}
\newcommand{\nats}{\N}
<!-- For terms being indexed.
Puts them in standard font face and creates an index entry.
arg: The term being defined.
\newcommand{\pointer}[1]{#1\index{#1}} -->
<!-- For bold terms to be index, but defined elsewhere
Puts them in bold face and creates an index entry.
arg: The term being defined. -->
\newcommand{\strong}[1]{\textbf{#1}}
<!-- For set names.
Puts them in italics. In math mode, yields decent spacing.
arg: The name of the set. -->
\newcommand{\set}[1]{\textit{#1}}
$$
@book{understanding,
abstract = {This volume is a theoretical and practical approach to the design of computer technology. The design and development of new technology is situated in an implicit understanding of human nature and work. The authors assert that the deep questions of design are those encountered when it is recognized that in designing tools we are designing new ways of being.},
added-at = {2011-01-18T10:24:55.000+0100},
address = {Norwood, NJ},
author = {Winograd, Terry and Flores, Fernando},
biburl = {http://www.bibsonomy.org/bibtex/22e34e46d86dc13454ddee8141a759e09/stefan.strecker},
interhash = {e2d3cd75aa2dfc8f8707521386c4b88b},
intrahash = {2e34e46d86dc13454ddee8141a759e09},
keywords = {PhilosophyOfScience},
publisher = {Ablex},
timestamp = {2011-01-18T10:24:55.000+0100},
title = {Understanding Computers and Cognition: A New Foundation for Design},
year = {1986}
}