@inproceedings{SC02infinity,
 author = {Jitka Stříbrná and Ivana Černá},
 booktitle = {Electronic Notes in Theoretical Computer Science},
 editor = {A. Kucera and R. Mayr},
 issue = {6},
 publisher = {Elsevier Science Publishers},
 title = {Modifications of Expansion Trees for Weak Bisimulation in BPA},
 volume = {68},
 year = {2002}
}