opinion: AMERICAN MEDICAL ASSOCIATION et al. v. FEDERAL TRADE COMMISSION
  No. 80-1690.
  Argued January 11, 1982
  Decided March 23, 1982
  Newton N. Minow argued the cause for petitioners. With him on the briefs were Jack R. Bierig, David W. Carpenter, William J. Doyle, and Linda L. Randell.
  Howard E. Shapiro argued the cause for respondent. With him on the brief were Solicitor General Lee, Assistant Attorney General Baxter, Deputy Solicitor General Shapiro, Elliott Schulder, March Coleman, and L. Barry Costilo
  Peter M. Sfikas filed a brief for the American Dental Association as amicus curiae urging reversal.
  A brief for the’ State of Ohio et al. as amici curiae urging affirmance was. filed by William J. Brown, Attorney General of Ohio, and Eugene F. McShane, Charles.D. Weller, and Clifton E. Johnson, Assistant Attorneys General; Robert K. Corbin, Attorney General of Arizona; J. D. MacFarlane, Attorney General of Colorado, and Thomas P. McMahon, Assistant Attorney General; Carl R. Ajello, Attorney General of Connecticut, and Robert M. Larger and John R. Lacey, Assistant Attorneys General; Thomas J. Miller, Attorney General of Iowa, and John R. Perkins, Assistant Attorney General; Stephen H. Sachs, Attorney General of Maryland, and Charles 0. Monk II and Naomi F. Samet, Assistant Attorneys General; Warren Spannaus, Attorney General of Minnesota, and Stephen P. Kilgrijf, Special Assistant Attorney General; Paul L. Douglas, Attorney General of Nebraska, and Dale A. Comer, Assistant Attorney General; JejfBingaman, Attorney General of New Mexico, and James J. Wechsler and Richard H. Levin, Assistant Attorneys General; Robert Abrams, Attorney General of New York, and Lloyd Constantine, Assistant Attorney General; Rufus L. Edmisten, Attorney General of North Carolina, H. A. Cole, Jr., Special Deputy Attorney General, and Fred R. Gamin, Assistant Attorney General; Leroy S. Zimmerman, Attorney General of Pennsylvania, and Carl S. Hisiro, Deputy Attorney General; Dennis J. Roberts II, Attorney General of Rhode Island, and Patrick J. Quinlan, Special Assistant Attorney General; and Chauncey H. Browning, Attorney General of West Virginia, and Charles G. Brown, Deputy Attorney General.
  Per Curiam.
  The judgment is affirmed by an equally divided Court.
  Justice Blackmun took no part in the consideration or decision of this case.