@article{10_4064_fm_89_2_111_130,
     author = {Solomon Feferman},
     title = {Two notes on abstract model theory. {II.} {Languages} for which, the set of valid sentences is semi-invariantly implicitly definable},
     journal = {Fundamenta Mathematicae},
     pages = {111--130},
     publisher = {mathdoc},
     volume = {89},
     number = {2},
     year = {1975},
     doi = {10.4064/fm-89-2-111-130},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-89-2-111-130/}
}