Reference:

J. Esparza, P. Rossmanith, and S. Schwoon. A uniform framework for problems on context-free grammars. EATCS Bulletin, 72:169–177, October 2000.

Suggested BibTeX entry:

@article{ERS00,
    author = {J. Esparza and P. Rossmanith and S. Schwoon},
    journal = {EATCS Bulletin},
    month = {October},
    pages = {169--177},
    title = {A Uniform Framework for Problems on Context-Free Grammars},
    volume = {72},
    year = {2000}
}