@article{PORMA_1994__51_2_47139,
     author = {Fountain, John and Gomes, Gracinda M.S.},
     title = {Proper left type- covers.},
     journal = {Portugaliae mathematica},
     pages = {305--319},
     publisher = {mathdoc},
     volume = {51},
     number = {2},
     year = {1994},
     zbl = {0812.20043},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1994__51_2_47139/}
}