Richard Beigel, Judy Goldsmith. Downward Separation Fails Catastrophically for Limited Nondeterminism Classes. SIAM Journal on Computing, 27(5):1420-1429, 1998. [doi]
@article{BeigelG98,
title = {Downward Separation Fails Catastrophically for Limited Nondeterminism Classes},
author = {Richard Beigel and Judy Goldsmith},
year = {1998},
url = {http://epubs.siam.org/sam-bin/dbq/article/27742},
researchr = {https://researchr.org/publication/BeigelG98},
cites = {0},
citedby = {0},
journal = {SIAM Journal on Computing},
volume = {27},
number = {5},
pages = {1420-1429},
}