@article{PORMA_1981__40_4_115466,
     author = {Haimo, Franklin},
     title = {Free subgroups in the endomorphism ring of an {Abelian} free group},
     journal = {Portugaliae mathematica},
     pages = {393--398},
     publisher = {mathdoc},
     volume = {40},
     number = {4},
     year = {1981},
     mrnumber = {0836100},
     zbl = {0581.20024},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1981__40_4_115466/}
}