%0 Journal Article
%A Feferman, Solomon
%T Persistent and invariant formulas for outer extensions
%J Compositio Mathematica
%D 1968
%P 29-52
%V 20
%I Wolters-Noordhoff Publishing
%U http://www.numdam.org/item/CM_1968__20__29_0/
%G en
%F CM_1968__20__29_0