Marcelo P. Fiore Roberto Di Cosmo Vincent Balat Remarks on isomorphisms in typed lambda calculi with empty and sum types. 35-50 2006 141 Ann. Pure Appl. Logic 1-2 http://dx.doi.org/10.1016/j.apal.2005.09.001 db/journals/apal/apal141.html#FioreCB06