@article{SF_1997__54_2_135520,
     author = {A. Cherubini and J. Meakin and B. Piochi},
     title = {Amalgams of free inverse semigroups.},
     journal = {Semigroup forum},
     pages = {199--220},
     publisher = {mathdoc},
     volume = {54},
     number = {2},
     year = {1997},
     zbl = {0872.20049},
     url = {http://geodesic.mathdoc.fr/item/SF_1997__54_2_135520/}
}