Ker-I Ko, Wen-Guey Tzeng. Three Sigma^p_2-Complete Problems in Computational Learning Theory. Computational Complexity, 1:269-310, 1991.
@article{KoT91,
title = {Three Sigma^p_2-Complete Problems in Computational Learning Theory},
author = {Ker-I Ko and Wen-Guey Tzeng},
year = {1991},
researchr = {https://researchr.org/publication/KoT91},
cites = {0},
citedby = {0},
journal = {Computational Complexity},
volume = {1},
pages = {269-310},
}