 Recall that the last three properties mentioned above — Dedekind completeness, well-ordering, and the finite interval property — are not definable by first-order sentences, but they can be expressed by temporal formulae. On the other hand, some very simple properties of temporal frames that are first-order definable, such as irreflexivity or anti-symmetry, are not expressible in TL. For more on temporal axioms expressing properties of time and details on such results, see Segerberg (1970); Rescher and Urquhart (1971); Burgess (1979); van Benthem (1983; 1995); Goldblatt (1992); and Hodkinson and Reynolds (2006).