Nicholas Pippenger, Michael J. Fischer
Journal of the ACM
The n-dimensional origin-crossing language, On, is a language each of whose words describes a walk through n-dimensional space beginning and ending at the origin. For each n, On is real-time recognizable by an n-counter machine but not by any (n - 1)-counter machine. In contrast, for all n, On is real-time recognizable by a one-tape Turing machine. © 1968 Springer-Verlag New York Inc.
Nicholas Pippenger, Michael J. Fischer
Journal of the ACM
Arnold L. Rosenberg, Lawrence Snyder
Mathematical Systems Theory
Zeev Barzilai, Don Coppersmith, et al.
IEEE TC
Arnold L. Rosenberg
POPL 1973