@article{gurevich1969the,
author = {Gurevich, Yuri},
title = {The Decision Problem for Decision Problems},
year = {1969},
month = {August},
abstract = {Consider the collection D of first-order formulas α such that the first-order theory with axiom α is decidable. It is proven that D is neither r.e. nor co-r.e. (The second part has been known earlier.)},
url = {http://approjects.co.za/?big=en-us/research/publication/decision-problem-decision-problems/},
pages = {362-363},
journal = {Algebra and Logic},
volume = {8},
}