The first edition of Class H, Social Sciences, was published in 1910, the secondin 1920, the third in 1949. The latter edition was reprinted in 1967 with supplementary pages of additions and changes. For the fourth edition, Class H was separated into two parts: H-HJ (Economics), published in 1981, and HM-HX (Sociology), published in 1980. With the 1994 edition, the two parts were reunited into a single volume. The 1997 edition incorporated changes made between 1994 and 1997, and contained a simplified subclass HJ as well as other revisions. The 2002 edition cumulated changes made between 1997 and 2002. The 2004 edition cumulated changes made between 2002 and May 2004, and included many updates to terminology used in captions. Editions published in 2005 and 2007 cumulated additions and changes that were made during the periods 2004-2005, and 2005-2006, respectively. The 2008 edition cumulated additions and changes that were approved during the period October 2006-June 2008.