@unpublished{ad2016e,
 author = {R. Kelly and
           B. A. Pearlmutter and
           J. M. Siskind},
 title = {Evolving the Incremental $\lambda$ Calculus into a Model of Forward
          {AD}},
 note = {Extended abstract, presented at the International Conference on
         Algorithmic Differentiation (AD)},
 location = {Oxford, UK},
 date = {12--15},
 month = sep,
 year = 2016,
 url = {http://engineering.purdue.edu/~qobi/papers/ad2016e.pdf}}