@incollection{iiasa4748,
       booktitle = {Models for Infectious Human Diseases: Their Structure and Relation to Data},
          editor = {V. Isham and G. Medley},
           title = {The saturating contact rate in epidemic models},
         address = {Cambridge},
       publisher = {Cambridge University Press},
            year = {1996},
             url = {https://pure.iiasa.ac.at/id/eprint/4748/},
            isbn = {0-521-45339-9},
          author = {Heesterbeek, J. A. P. and Metz, J. A. J.}
}