To cite the \emph{ probit.survey } Zelig model:
 \begin{verse}
 Nicholas Carnes. 2008. "probit.survey: Survey-Weighted Probit Regression for Dichotomous Dependent Variables" in Kosuke Imai, Gary King, and Olivia Lau, "Zelig: Everyone's Statistical Software,"\url{http://gking.harvard.edu/zelig} 
\end{verse}