Reference:

J. Esparza and C. Schröter. Unfolding based algorithms for the reachability problem. Fundamenta Informaticae, 47(3–4):231–245, 2001.

Suggested BibTeX entry:

@article{ES02,
    author = {J. Esparza and C. Schr{\"o}ter},
    journal = {Fundamenta Informaticae},
    number = {3--4},
    pages = {231--245},
    title = {Unfolding Based Algorithms for the Reachability Problem},
    volume = {47},
    year = {2001}
}