“…As a closing note let us briefly mention that quite recently, several papers appeared which are related to different other aspects of the study of (2 + 1)-dimensional gravity: In [25] and [26], massive gravity and supergravity are discussed; in [27], higher spin in topologically massive gravity is discussed; in [28] and [29] wormholes and star models are constructed in 2+1 dimensions; in [30], Birkhoff's theorem is generalized; in [31], [32], [33], [34], [35], [36], [37], and [38] various properties of the BTZ geometry are discussed; in [39], massive particles with spin in 2 + 1 dimension are constructed; in [40], [41], [42], [43], and [44] further aspects of (2 + 1)-dimensional gravity are deduced and discussed; and finally in [45], the observability of strong gravitational sources (black hole, naked singularities) via lensing is discussed.…”