@article{MZ_1979__168_172860,
     author = {Heiner Zieschang and Edelgard Gramberg},
     title = {Order {Reduced} {Reidemeister-Schreier} {Subgroup} {Presentations} and {Applications.}},
     journal = {Mathematische Zeitschrift},
     pages = {53--70},
     publisher = {mathdoc},
     volume = {168},
     year = {1979},
     zbl = {0388.20027},
     url = {http://geodesic.mathdoc.fr/item/MZ_1979__168_172860/}
}