Mariangiola Dezani-Ciancaglini Paula Severi Fer-Jan de Vries Infinitary lambda calculus and discrimination of Berarducci trees. 275-302 2003 2 Theor. Comput. Sci. 298 http://dx.doi.org/10.1016/S0304-3975(02)00809-5 db/journals/tcs/tcs298.html#Dezani-CiancagliniSV03