To cite the \emph{ gamma.net } Zelig model:
 \begin{verse}
 Skyler J. Cranmer. 2007. "gamma.net: Social Network Gamma Regression for Continuous, Positive Dependent Variables" in Kosuke Imai, Gary King, and Olivia Lau, "Zelig: Everyone's Statistical Software,"\url{http://gking.harvard.edu/zelig} 
\end{verse}