- Cristian Caluce, Ion Chiţescu, “A combinatorial characterization of sequential p. martin-löf tests”, International Journal of Computer Mathematics, 17, no. 1, 1985, 53
- Gaisi Takeuti, Masahiro Yasumoto, Gödel '96, 2017, 120
- Vladimir A. Zakharov, 2055, Machines, Computations, and Universality, 2001, 133
- L. A. Bokut', G. P. Kukin, “Unsolvable algorithmic problems for semigroups, groups, and rings”, J Math Sci, 45, no. 1, 1989, 871