# Putting two derivations on the same line

I'm trying to put two logic derivations on the same line, but I'm having trouble figuring out how to do this. Here is a sample of the code that I'm using:

\documentclass{article}
\usepackage{bussproof}

\begin{document}
\begin{center}
%derivation 1
\AxiomC{$\Gamma, \varphi \mid \psi$}
\UnaryInfC{$\Gamma, \neg\neg\varphi \mid \neg\neg\psi$}
\DisplayProof

%derivation 2
\AxiomC{$\Gamma, \neg\neg\varphi \mid \neg\neg\psi$}
\UnaryInfC{$\Gamma, \varphi \mid \psi$}
\DisplayProof
\end{center}
\end{document}

I'd like both derivations to be centered and on the same line. Thanks in advance for your help.

The easiest method is to place the derivations in separate minipages:

\documentclass{article}
\usepackage{bussproofs}

\begin{document}
\begin{center}
\begin{minipage}{.5\columnwidth}
%derivation 1
\AxiomC{$\Gamma, \varphi \mid \psi$}
\UnaryInfC{$\Gamma, \neg\neg\varphi \mid \neg\neg\psi$}
\DisplayProof
\end{minipage}% <--- or a space would be inserted
\begin{minipage}{.5\columnwidth}
%derivation 2
\AxiomC{$\Gamma, \neg\neg\varphi \mid \neg\neg\psi$}
\UnaryInfC{$\Gamma, \varphi \mid \psi$}
\DisplayProof
\end{minipage}
\end{center}
\end{document}

Reduce the fraction of \columnwidth if you want them nearer to each other.

Alternatively, set them inside a box:

\documentclass{article}
\usepackage{bussproofs}

\begin{document}
\begin{center}
%derivation 1
\mbox{\AxiomC{$\Gamma, \varphi \mid \psi$}
\UnaryInfC{$\Gamma, \neg\neg\varphi \mid \neg\neg\psi$}
\DisplayProof}%
\hspace{4em}% or whatever space you like
%derivation 2
\mbox{\AxiomC{$\Gamma, \neg\neg\varphi \mid \neg\neg\psi$}
\UnaryInfC{$\Gamma, \varphi \mid \psi$}
\DisplayProof}
\end{center}
\end{document}