Key points are not available for this paper at this time.
After the enthusiasm raised by the discovery of multiple quasars and a few years later of giant luminous arcs in clusters of galaxies, gravitational lensing has proven to be a versatile tool to study a broad range of astrophysical problems. I will illustrate recent results obtained in several domains such as: the mass determination for galaxies and clusters of galaxies, the mapping of large scale structures, and the use of lenses to constrain the Hubble constant.
G. Soucail (Mon,) studied this question.