@article{1093958337,
author = {Weston, Kenneth},
title = {On predicate letter formulas which have no substitution instances provable in a first order language.},
journal = {Notre Dame J. Formal Logic},
volume = {6},
number = {1},
year = {1965},
pages = { 296-300},
language = {en},
url = {http://dml.mathdoc.fr/item/1093958337}
}
Weston, Kenneth. On predicate letter formulas which have no substitution instances provable in a first order language.. Notre Dame J. Formal Logic, Tome 6 (1965) no. 1, pp. 296-300. http://gdmltest.u-ga.fr/item/1093958337/