To cite the \emph{ ei.RxC } Zelig model:
 \begin{verse}
 Jason Wittenberg, Ferdinand Alimadhi, Badri Narayan Bhaskar, and Olivia Lau. 2007. "ei.RxC: Hierarchical Multinomial-Dirichlet Ecological Inference Model for R x C Tables" in Kosuke Imai, Gary King, and Olivia Lau, "Zelig: Everyone's Statistical Software,"\url{http://gking.harvard.edu/zelig} 
\end{verse}