 For further philosophical discussion on first-order modal and temporal logics, see Rescher and Urquhart (1971, Chapter XX); McArthur (1976); Garson (1984): Linsky and Zalta (1994); van Benthem (1995, Section 7); Fitting and Mendelsohn (1998); Wölfl (1999); Cocchiarella (2002); as well as Lindström and Segerberg (2006).