Synthetic Aperture Sonar (SAS) is a promising new technique for application in small Unmanned Underwater Vehicles (UUV) for future mine-hunting operations. The relatively short array in a UUV can be synthetically extended to obtain higher resolution and more array gain, leading to improved detection, classification and localisation of mines. Unlike its radar equivalent Synthetic Aperture Radar (SAR) the SAS technique is not yet mature. On the contrary, SAS is still very much unproven, while SAR has already been operational for many years. As a consequence, literature on SAR is abundant, but on SAS relatively rare. This report gives an overview of relevant literature, in which the most fundamental problems of SAS are reviewed.