Hausman, J. A., B. H. Hall, and Z. Griliches (1984): "Econometric Models for Count Data with an Application to the Patents-R&D Relationship." Econometrica (46), pp. 909–938
Cameron, C. A. and P. K. Trivedi (2015) "Count Panel Data," Oxford Handbook of Panel Data, ed. by B. Baltagi, Oxford University Press, pp. 233–256
Wooldridge, J. (2002): Econometric Analysis of Cross Section and Panel Data, MIT Press, Cambridge, Mass.
Andersen, E. B. (1970): "Asymptotic Properties of Conditional Maximum Likelihood Estimators." Journal of the Royal Statistical Society, Series B, 32, pp. 283–301
Wooldridge, J. M. (1999): "Distribution-Free Estimation of Some Nonlinear Panel Data Models." Journal of Econometrics (90), pp. 77–97