 Detailed accounts of the full abstraction problem for PCF can be found in Gunter 1992 (chaps 5,6), Streicher 2006, Ong 1995, Stoughton 1988 and Amadio &amp; Curien 1998 (chaps 6, 12, 14), in approximately increasing order of technical complexity. The emphasis on the recursion-theoretic aspects of PCF and its full abstraction problem are dealt with in detail in the textbook (Longley &amp; Normann 2015: chaps 6, 7); a shorter account can be found in Longley 2001 (sec. 4).