added citation for UB formalism

doc/formulas/formulas.tex

@@ -207,8 +207,13 @@ Special case for cubic crystals, $g_{ij} = \delta_{ij} \cdot \left( 2\pi / a \ri
 
 
 
+\section{Bibliographic information}
 
-%\bibliographystyle{alpha}
-%\bibliography{\jobname.bib}
+The UB matrix formalism to convert between relative lattice units and laboratory or instrument coordinates is described in \cite{Lumsden2005}.
+
+
+
+\bibliographystyle{alpha}
+\bibliography{\jobname.bib}
 
 \end{document}