Reference:

Stefan Kiefer. BPA bisimilarity is EXPTIME-hard. Information Processing Letters (IPL), 113(4):101–106, 2013.

Abstract:

Given a basic process algebra (BPA) and two stack symbols, the BPA bisimilarity problem asks whether the two stack symbols are bisimilar. We show that this problem is EXPTIME-hard.

Suggested BibTeX entry:

@article{13K:IPL,
    author = {Stefan Kiefer},
    journal = {Information Processing Letters (IPL)},
    number = {4},
    pages = {101--106},
    title = {{BPA} bisimilarity is {EXPTIME}-hard},
    volume = {113},
    year = {2013}
}