In 2000 we proposed a sociophysics model of opinion formation, which was based on trade union maxim ``United we Stand, Divided we Fall'' (USDF) and latter due to Dietrich Stauffer became known as the Sznajd model (SM). The main difference between SM compared to voter or Ising-type models is that information flows outward. In this paper we review the modifications and applications of SM that have been proposed in the literature.

PACS numbers: 05.50.+q, 89.65.--s