Reference:

Allan Cheng, Javier Esparza, and Jens Palsberg. Complexity results for 1-safe nets. Theoretical Computer Science, 147(1&2):117–136, 1995.

Suggested BibTeX entry:

@article{tcs95,
    author = {Allan Cheng and Javier Esparza and Jens Palsberg},
    journal = {Theoretical Computer Science},
    number = {1{\&}2},
    pages = {117-136},
    title = {Complexity Results for 1-Safe Nets},
    volume = {147},
    year = {1995}
}