Franck van Breugel Claudio Hermida Michael Makkai James Worrell Recursively defined metric spaces without contraction. 143-163 2007 380 Theor. Comput. Sci. 1-2 http://dx.doi.org/10.1016/j.tcs.2007.02.059 db/journals/tcs/tcs380.html#BreugelHMW07