@article{RCM_1985__19_181749,
     author = {Solomon Feferman},
     title = {A {Theory} {Of} {Variable} {Types.}},
     journal = {Revista colombiana de matematicas},
     pages = {95--106},
     publisher = {mathdoc},
     volume = {19},
     year = {1985},
     zbl = {0615.03045},
     url = {http://geodesic.mathdoc.fr/item/RCM_1985__19_181749/}
}