@unpublished{ad2016b,
 author = {J. M. Siskind and
           B. A. Pearlmutter},
 title = {Efficient Implementation of a Higher-Order Language with Built-In
          {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/ad2016b.pdf}}