Bibliography - Increase horizontal white space after each entry

Question

I would like to change the layout of my bibliography as follows:

Minimal Working Example Tex-File:

\documentclass{article}
\begin{document}

\title{My Article}
\author{Nobody Jr.}
\date{Today}
\maketitle

Blablabla said Nobody ~\cite{bressoud1989factorization}.


\bibliography{Master}
\bibliographystyle{alpha}

\end{document}

Master.bib:

@book{bressoud1989factorization,
  title={Factorization and Primality Testing},
  author={Bressoud, D.M.},
  isbn={9780387970400},
  lccn={89019690},
  series={Undergraduate Texts in Mathematics},
  year={1989},
  publisher={Springer}
}

Answer 1

Internally the thebibliography environment uses a list, so you can change the value for \labelsep (controlling the separation between the label and the entries); the quickest way for doing so is to patch the command with the help of, for example, etoolbox (instead of 20pt use the length that best suits your needs):

\begin{filecontents*}{Master.bib}
@book{bressoud1989factorization,
  title={Factorization and Primality Testing},
  author={Bressoud, D.M.},
  isbn={9780387970400},
  lccn={89019690},
  series={Undergraduate Texts in Mathematics},
  year={1989},
  publisher={Springer}
}
@book{bressoud1990,
  title={Another Factorization and Primality Testing},
  author={Bressoud, D.M.},
  isbn={9780387970400},
  lccn={89019690},
  series={Undergraduate Texts in Mathematics},
  year={1990},
  publisher={Springer}
}
\end{filecontents*}
\documentclass{article}
\usepackage{etoolbox}

\patchcmd{\thebibliography}{\leftmargin\labelwidth}{\leftmargin\labelwidth\labelsep=20pt}{}{}

\begin{document}

\nocite{*}

\bibliographystyle{alpha}
\bibliography{Master}

\end{document}