Barak A. Pearlmutter Jeffrey Mark Siskind Reverse-mode AD in a functional framework: Lambda the ultimate backpropagator. 2008 30 ACM Trans. Program. Lang. Syst. 2 http://doi.acm.org/10.1145/1330017.1330018 db/journals/toplas/toplas30.html#PearlmutterS08