Dex One Corporation provides online, mobile and print search marketing via their DexKnows.com website, print yellow pages directories and pay-per-click ad networks in the U.S.

Dex One Corporation was formed in February 2010. It was previously the R. H. Donnelley Company, which was founded in 1886 by Reuben H. Donnelley, son of RR Donnelley founder Richard R. Donnelley, as The Chicago Directory Company. Donnelley primarily contracted with The Chicago Telephone Company to publish telephone directories for Chicago Telephone customers. In 1906, however, Donnelley would venture outside Chicago, contracting with Bell System firms such as New York Telephone, Wisconsin Telephone, and Cincinnati Suburban Telephone Co.

In 1917, The Reuben H. Donnelley Company was incorporated and moved to New York City, retaining some offices in Chicago. In 1925, Donnelley died, leaving behind his company which continued to contract with the Bell System to publish telephone directories.

In 1961, Dun & Bradstreet Corp merged with R.H. Donnelley with R.H. Donnelley becoming a wholly owned subsidiary.

Dex may refer to:

Barbara Deckx (born 22 January 1974 in Turnhout), better known by her stage name Barbara Dex, is a Belgian singer who represented her country in the 1993 Eurovision Song Contest with the song "Iemand als jij". Dex had qualified via the Belgian national heat, Eurosong 93, held at the Casino Knokke on March 6. At the Eurovision in Millstreet, she won seventh spot, after Greece's entry "Eladha, Hora Tu Fotos" and before Malta's song "This Time". Dex came 25th and last.

Barbara returned to the Belgian final in 2004, teaming up with Alides for the song "One Life" which was placed third. A further Eurovision attempt came in 2006 with the country line-dancing flavoured "Crazy" which earned her the fifth place.

Barbara Dex is one of three children of Marcel Deckx, a Belgian singer better known by his stage name Marc Dex. Her brother Tom Deckx has played bass guitar in the musical groups Tush and Nuts.

Dex has released several albums between 1993 and 2011.

First album "Iemand" contains songs in Dutch. Since 1994 she sings only in English.