@inproceedings{rosu-2006-icfp,
title={Equality of Streams is a $Pi_2^0$-Complete Problem},
author={Grigore Ro\c{s}u},
booktitle={Proceedings of the 11th ACM SIGPLAN International Conference on Functional Programming (ICFP'06)},
publisher={ACM},
year="2006"
}