%0 Journal Article %A Gert Denk %A Wolfgang Metzler %T Nielsen reduction in free groups with operators %J Fundamenta Mathematicae %D 1988 %P 181-197 %V 129 %N 3 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.4064/fm-129-3-181-197/ %R 10.4064/fm-129-3-181-197 %G en %F 10_4064_fm_129_3_181_197