Inc, Nielsen Business Media (1998-09-26). Billboard. Nielsen Business Media, Inc. p. 24. elephant parts billboard.{{cite book}}: |last= has generic name (help)
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Inc, Nielsen Business Media (1982-06-12). Billboard. Nielsen Business Media, Inc. {{cite book}}: |last= has generic name (help)
Inc, Nielsen Business Media (1983-02-19). Billboard. Nielsen Business Media, Inc. {{cite book}}: |last= has generic name (help)