 The main works surveyed in this section are Reichenbach 1956, Suppes 1970, Cartwright 1979, Skyrms 1980, and Eells 1991. Williamson 2009 and Hitchcock 2016 are two further surveys that cover a number of the topics discussed in this section. The entries for  Hans Reichenbach  and  Reichenbach’s Common Cause Principle  include discussions of Reichenbach’s program and the status of his Common Cause Principle. Salmon (1984) contains an extensive discussion of conjunctive forks. The entry for  Simpson’s paradox  contains further discussion of some of the issues raised in  Section 2.4.