1. Recursive equivalence types;Dekker, J. C. E.;Univ. California Publ. Math.,1960
2. Infinite series of isols;Dekker, J. C. E.,1962
3. The minimum of two regressive isols;Dekker, J. C. E.;Math. Z.,1964
4. Extensions to isols;Nerode, Anil;Ann. of Math. (2),1961