210 5. Exact Groups and Related Topics
[6] for more. The Gromov boundary of a hyperbolic space was defined by-
care to guess? -Gromov. Theorem 5.3.15 is due to Adams, but our proof is
taken from [96]. Proposition 5.3.18 and its Akemann-Ostrand corollary are
explicit in [85], though previously known to Germain, Skandalis and per-
haps others. Roe's lecture notes [167] on coarse geometry contain far more
information than covered here (including connections with Baum-Connes
conjectures). The fact that nuclearity of the uniform Roe algebra implies
property A was proved in [1 77], using different methods than those in these
notes. Finally, see the books [6], [140] and [164] for all things groupoid.