# Putting citation on right side of the equation

I have written an equation in LaTeX and I need to cite the author name with date (Einstein 1915) on the right side of my equation, I tried with the margin note command but it gets split in two lines, how do I get it in one line just right-below my equation?

• Please edit you post and show us an minimal example of what you have tried. In the current form, we will have to guess around. – LaRiFaRi Aug 4 '14 at 10:54

Use the \tag command from the mathtools package (useless to load amsmath in that case). If you don't want the parentheses, use \ tag*:

    \documentclass[12pt,a4paper,bothsides]{article}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{fourier}
\usepackage{mathtools}

\begin{document}

\begin{gather}
E = mc^{2}\tag{Einstein 1915}\\
E = mc^{2}\tag*{Einstein 1915}
\end{gather}

\end{document}