What happens when NEWSPAPERS DEPARTMENT-STORE SALES NOSEDIVE during newspaperless October. Comparisons are vs, 1948 since major coal and steel strikes in late 1949 make ’SO-’49 comparisons uninforma tive. Bars show change up or down in combined net sales of 10 key Pittsburgh stores as compiled by University of Pittsburgh’s Bureau of Business Research. Newspapers’ absence, reported a spokesman for one of Pittsburgh’s top retailers, “forced us into other media which haven’t come within miles of justifying their cost in terms of results,’’ an experience lew cities ever face. But from