@article{RSMUP_1984__72__231_0,
     author = {Maier, Berthold J.},
     title = {Amalgams of torsion-free nilpotent groups of class three},
     journal = {Rendiconti del Seminario Matematico della Universit\`a di Padova},
     pages = {231--247},
     publisher = {Seminario Matematico of the University of Padua},
     volume = {72},
     year = {1984},
     mrnumber = {778343},
     zbl = {0559.20020},
     language = {en},
     url = {http://archive.numdam.org/item/RSMUP_1984__72__231_0/}
}