Justice Dept. Seeks A.C. Nielsen Documents: A.C. Nielsen Co., a unit of Dun & Bradstreet, said the Justice Department has asked it for documents concerning its syndicated sales tracking services. The documents relate to a civil investigation that "will enable the department to evaluate the competitive nature of certain market behavior," Schaumburg, Ill.-based Nielsen said. "Our understanding of the CID (civil investigation demand) is it is to help the Justice Department evaluate the marketplace but in no way implies any wrongdoing on the part of Nielsen," a spokesman said. "Nielsen competes vigorously in all parts of the business."