I wanted to make a readable bibliography which uses as less space as possible, something like this:

I modified the A&A natbib style package to have something like that, here is the code (rename bib.txt to proposal.bst). You need to put it into your latex as:
\usepackage[numbers, sort&compress]{natbib}
\bibliographystyle{proposal}
\usepackage{paralist}
\renewenvironment{thebibliography}[1]{
\section*{\refname}
\let\par\relax\let\newblock\relax
\let\olditem\item
\renewcommand{\item}[1][]{ \textbullet\ \textbf{\olditem} }
\inparaenum}{\endinparaenum}
This create citations of the type “[1]”, which are the shortest. They are listed in order of appearance. To add the bibliography then I use:
{\footnotesize
\renewcommand{\section}[2]{} % remove title
\setlength{\bibsep}{0.0pt}
\bibliography{bib}
}