Complex sentence: On July 1,1998, D&B spins off R. H. Donnelley into a separate, publicly-traded company beginning to trade under RHD on the NYSE under the "RHD" symbol.
Split into simpler sentences: On July 1,1998, D&B spins off R. H. Donnelley into a separate, publicly-traded company. RHD then begins trading on the NYSE under the "RHD" symbol.