@article{10_1017_S204061850003522X,
     author = {Dey, I. M. S.},
     title = {Schreier systems in free products},
     journal = {Glasgow mathematical journal},
     pages = {61--79},
     year = {1965},
     volume = {7},
     number = {2},
     doi = {10.1017/S204061850003522X},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S204061850003522X/}
}