How do I get the author and the year in square brackets?

Question

I have to following problem. I'm working on a presentation. Therefore I need, when I cite a paper or something else, the whole name and year of the paper. Everything went well until now. When I cite something it is displayed like this:

Donald Knuth [1995]

But I want it this way:

[Donald Knuth, 1995]

This is my preamble:

\documentclass{beamer}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage{amsmath,amsfonts,amssymb}
\usepackage[square,sort,comma,super,authoryear]{natbib}
\usepackage{url}
\usepackage{color}
\usepackage{tikz}
\bibliographystyle{plainnat}
\def\newblock{} % To avoid a compilation error about a function \newblock undefined

Answer 1

You have to use \citep; here's a complete example.

\begin{filecontents*}{\jobname.bib}
@book{knuth1995,
 author={Donald E. Knuth},
 title={The {\TeX}book},
 year={1995},
}
\end{filecontents*}

\documentclass{beamer}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[ngerman]{babel}
\usepackage[square,sort,comma,super,authoryear]{natbib}

\begin{document}
\begin{frame}
\citep{knuth1995}

\bibliographystyle{plainnat}

\begin{block}{\refname}
\bibliography{\jobname}
\end{block}
\end{frame}

\end{document}