Scrypt is maximally memory hard
J.F. Alwen, B. Chen, K.Z. Pietrzak, L. Reyzin, S. Tessaro, in:, J.-S. Coron, J. Buus Nielsen (Eds.), Springer, 2017, pp. 33–62.

Depth-robust graphs and their cumulative memory complexity
J.F. Alwen, J. Blocki, K.Z. Pietrzak, in:, J.-S. Coron, J. Buus Nielsen (Eds.), Springer, 2017, pp. 3–32.