Cosmic Topology : Twenty Years After
  What is the shape of the Universe? Is it finite or infinite ? Is space
multi-connected to create ghost images of faraway cosmic sources? After a "dark
age" period, the field of cosmic topology has now become one of the major
concerns in astronomy and cosmology, not only from theorists but also from
observational astronomers. Here I give a personal account of the spectacular
progress in the field since the beginning of the 1990's, when I started to work
in it.
