Kevin Donnelly Hongwei Xi A Formalization of Strong Normalization for Simply-Typed Lambda-Calculus and System F. 109-125 2007 174 Electr. Notes Theor. Comput. Sci. 5 http://dx.doi.org/10.1016/j.entcs.2007.01.021 db/journals/entcs/entcs174.html#DonnellyX07