Regan, Kenneth W. (1996). "Linear time and memory-efficient computation". SIAM Journal on Computing. 25 (1): 133–168. doi:10.1137/S0097539793251888.
Hühne, Martin (1993). "Linear Speed-Up Does not Hold on Turing Machines with Tree Storages". Information Processing Letters. 47 (6): 313–318. doi:10.1016/0020-0190(93)90078-N.