René David Karim Nour Why the Usual Candidates of Reducibility Do Not Work for the Symmetric <i>lamba-my</i>-calculus. 101-111 2005 140 Electr. Notes Theor. Comput. Sci. http://dx.doi.org/10.1016/j.entcs.2005.06.020 db/journals/entcs/entcs140.html#DavidN05