@article{IM_1988__94_2_143618,
     author = {Stephen G. Brick},
     title = {Normal-convexity and equations over groups.},
     journal = {Inventiones mathematicae},
     pages = {81--104},
     publisher = {mathdoc},
     volume = {94},
     number = {2},
     year = {1988},
     zbl = {0655.20025},
     url = {http://geodesic.mathdoc.fr/item/IM_1988__94_2_143618/}
}