@unpublished{nepls2005,
 author = {J. M. Siskind},
 title = {Taking Derivatives of Functional Programs: AD in a Functional
          Framework},
 location = {New England Programming Languages and Systems (NEPLS)},
 date = 27,
 month = oct,
 year = 2005,
 url = {http://engineering.purdue.edu/~qobi/tweet-talks/nepls2005-slides.pdf}}