A few more citations

[davidBelanger]

This is a great package! Thanks for making it available.

FYI, your README should cite a few more works:

Zweig, Geoffrey and Padmanabhan, Mukund. Exact Alpha-Beta Computation in
Logarithmic Space with Application to MAP Word Graph Construction. Sixth
International Conference on Spoken Language Processing, 2000.

Lewis, Bil. Debugging Backwards in Time. arXiv preprint cs/0310016, 2003.

[yaroslavvb]

Would you like to send a PR for that?

Also, Griewank describes similar memory saving techniques in his AD work in the 1990s, they are summarized in Evaluating derivatives: principles and techniques of algorithmic differentiation