Thomas Ehrhard A relative PCF-definability result for strongly stable functions and some corollaries. 2000 35 Electr. Notes Theor. Comput. Sci. http://www.elsevier.com/gej-ng/31/29/23/65/22/show/Products/notes/index.htt#007 db/journals/entcs/entcs35.html#Ehrhard00