To cite the \emph{ oprobit.bayes } Zelig model:
 \begin{verse}
 Ben Goodrich and Ying Lu. 2007. "oprobit.bayes: Bayesian Ordered Probit Regression" in Kosuke Imai, Gary King, and Olivia Lau, "Zelig: Everyone's Statistical Software,"\url{http://gking.harvard.edu/zelig} 
\end{verse}